Document and Entity Information [Abstract] Statement [Table] Class of Stock [Axis] Class Of Stock [Domain] Class of Stock [Domain] Common Class A [Member] Common Class A Common Class B [Member] Common Class B Statement [Line Items] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Consolidated Balance Sheets Assets [Abstract] ASSETS Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value CASH AND CASH EQUIVALENTS-End of year CASH AND CASH EQUIVALENTS-Beginning of year Cash and cash equivalents Available-for-sale Securities, Debt Securities, Current Short-term marketable securities Total marketable securities, Aggregate Fair Value Accounts Receivable, Net, Current Accounts receivable, net Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Assets, Current Total current assets Restricted Cash and Cash Equivalents, Noncurrent Restricted cash Property, Plant and Equipment, Net Property and equipment, net Total property and equipment, net Intangible Assets, Net (Excluding Goodwill) Net Total Intangible assets, net Goodwill Balance at the end of the period Balance at the beginning of the period Goodwill Other Assets, Noncurrent Other long-term assets Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Accrued expenses and other current liabilities. Accrued Liabilities and Other Liabilities, Current Accrued expenses and other current liabilities Total accrued expenses and other current liabilities Deferred Revenue, Current Deferred revenue Liabilities, Current Total current liabilities Liabilities, Noncurrent Long-term liabilities Total long-term liabilities Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (Note 10) Stockholders' Equity Attributable to Parent [Abstract] Stockholders' equity: Preferred Stock, Value, Issued Preferred stock, $0.001 par value, 100,000,000 shares authorized, none issued Common Stock, Value, Issued Common stock, $0.001 par value per share: Authorized shares 1,100,000,000 as of December 31, 2017 and 2016; Issued and outstanding shares 93,969,796 and 87,248,548 as of December 31, 2017 and 2016 Additional Paid in Capital, Common Stock Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive income Retained Earnings (Accumulated Deficit) Accumulated deficit Stockholders' Equity Attributable to Parent Ending balance Beginning balance Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Preferred Stock Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, authorized (in shares) Shares Authorized (in shares) Preferred Stock, Shares Issued Preferred stock, issued (in shares) Shares Issued (in shares) Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Net Loss Per Share Attributable to Common Stockholders Common Stock Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, authorized (in shares) Common Stock, Shares, Issued Common stock, issued (in shares) Common Stock, Shares, Outstanding Common stock, outstanding (in shares) Consolidated Statements of Operations Revenues Revenue Cost of Revenue Cost of revenue Gross Profit Gross profit Operating Expenses [Abstract] Operating expenses: Research and Development Expense Research and development Selling and Marketing Expense Sales and marketing General and Administrative Expense General and administrative Amount of charitable contributions made by the entity during the period. Charitable Contribution Expense Charitable contribution Operating Expenses Total operating expenses Operating Income (Loss) Loss from operations Other Nonoperating Income (Expense) Other income (expenses), net Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest Loss before provision for income taxes Income Tax Expense (Benefit) Provision for income taxes Provision for income taxes Net Income (Loss) Attributable to Parent Net loss Net loss Deemed dividend to investors in relation to tender offer. Tender Offer to Investors, Deemed Dividend Deemed dividend to investors in relation to tender offer Net Income (Loss) Available to Common Stockholders, Basic Net loss Net loss attributable to common stockholders Net loss attributable to common stockholders Earnings Per Share, Basic and Diluted Net loss per share attributable to common stockholders, basic and diluted (in dollars per share) Net loss per share attributable to common stockholders, basic and diluted (in dollars per share) Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares) Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares) Consolidated Statements of Comprehensive Loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive income: Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Unrealized loss on marketable securities Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent Foreign currency translation Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total other comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss attributable to common stockholders Statement of Stockholders' Equity [Abstract] Sale of Stock [Axis] Sale Of Stock Name Of Transaction [Domain] Sale of Stock [Domain] Follow-on public offering. Follow On Public Offering [Member] Follow-on Public Offering Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Shares, Issued Ending balance (in shares) Beginning balance (in shares) Stock Issued During Period, Value, New Issues Issuance of stock Stock Issued During Period, Shares, New Issues Shares sold (in shares) Issuance of stock (in shares) Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs Costs related to public offerings Costs related to the public offerings Stock Issued During Period, Value, Conversion of Convertible Securities Conversion of convertible preferred stock to common stock in connection with initial public offering Stock Issued During Period, Shares, Conversion of Convertible Securities Shares issued upon automatic conversion (in shares) Conversion of convertible preferred stock to common stock in connection with initial public offering (in shares) Value of stock issued as a result of the exercise of vested stock options. Stock Issued During Period, Value, Stock Options Exercised, Vested Exercise of vested stock options Shares of stock issued as a result of the exercise of vested stock options. Stock Issued During Period, Shares, Stock Options Exercised, Vested Exercise of vested stock options (in shares) Adjustment to additional paid in capital vesting of early exercised stock options. Adjustment to Additional Paid in Capital, Vesting of Early Exercised Stock Options Vesting of early exercised stock options Number of shares issued during the period related to the vesting of Restricted Stock Units. Stock Issued During Period, Shares, Restricted Stock Units, Vesting Vesting of restricted stock units (in shares) Adjustments Related to Tax Withholding for Share-based Compensation Value of equity awards withheld for tax liability Shares Paid for Tax Withholding for Share Based Compensation Value of equity awards withheld for tax liability (in shares) Shares of stock issued as a result of the exercise of unvested stock options. Stock Issued During Period, Shares, Stock Options Exercised, Unvested Exercises of unvested stock options (in shares) Stock Repurchased During Period, Value Repurchase of shares in tender offer Stock Repurchased During Period, Shares Repurchase of shares in tender offer (in shares) Number of shares repurchased (in shares) Dividends Deemed dividend in relation to tender offer Equity impact of the conversion of shares of Class B common stock into shares of Class A common stock. Conversion of Classes of Common Stock, Equity Impact Conversion of shares of Class B common stock into shares of Class A common stock Conversion of shares of Class B common stock into shares of Class A common stock. Conversion of Classes of Common Stock Conversion of shares of Class B common stock into shares of Class A common stock (in shares) Stock Issued During Period, Value, Employee Stock Purchase Plan Shares issued under ESPP Stock Issued During Period, Shares, Employee Stock Purchase Plans Shares issued under ESPP (in shares) Value of shares issued during the period to donor-advised fund as a charitable contribution. Stock Issued During Period, Value, Donor-Advised Fund Twilio.org, reserved shares, issued fair value Donated common stock Number of shares issued during the period to a donor-advised fund as a charitable contribution. Stock Issued During Period, Shares, Donor-Advised Fund Twilio.org, reserved shares, issued (in shares) Donated common stock (in shares) Amount of unvested stock options repurchased. Stock Repurchased During Period, Value, Unvested Stock Options Repurchase of unvested stock options Shares of unvested stock options repurchased. Stock Repurchased During Period, Shares, Unvested Stock Options Repurchase of unvested stock options (in shares) Stock Issued During Period, Value, Acquisitions Issuance of Series T convertible preferred Stock in acquisition Stock Issued During Period, Shares, Acquisitions Issuance of Series T convertible preferred Stock in acquisition (in shares) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation Escrow shares returned to the issuer. Escrow Shares Returned to Issuer Escrow shares returned to the issuer (in shares) Preferred Stock, Including Additional Paid in Capital [Abstract] Consolidated Statements of Stockholders' Equity Stock issuance costs incurred during the period. Stock Issuance Costs Costs related to issuance of stock Consolidated Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities [Abstract] CASH FLOWS FROM OPERATING ACTIVITIES: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash provided by (used in) operating activities: Depreciation, Depletion and Amortization Depreciation and amortization Investment Income, Amortization of Premium Amortization of bond premium Share-based Compensation Stock-based compensation Noncash Contribution Expense Value of donated common stock Provision for Doubtful Accounts Provision for doubtful accounts Additions Tax benefit related to acquisition. Acquisition Tax Benefit Tax benefit related to acquisition Write off of internally developed software. Write off of Internally Developed Software Write-off of internal-use software Value of internally-developed software written-off due to abandonment Gain (Loss) on Contract Termination (Gain) loss on lease termination Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets Increase (Decrease) in Other Noncurrent Assets Other long-term assets Increase (Decrease) in Accounts Payable Accounts payable The increase (decrease) during the reporting period in the aggregate amount of accrued expenses and other current liabilities. Increase (Decrease) in Accrued Liabilities and Other Liabilities, Current Accrued expenses and other current liabilities Increase (Decrease) in Deferred Revenue Deferred revenue Increase (Decrease) in Other Noncurrent Liabilities Long-term liabilities Net Cash Provided by (Used in) Operating Activities Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] CASH FLOWS FROM INVESTING ACTIVITIES: Increase (Decrease) in Restricted Cash (Increase) decrease in restricted cash Payments to Acquire Available-for-sale Securities, Debt Purchases of marketable securities Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Maturities of marketable securities Payments to Develop Software Capitalized software development costs Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Payments to Acquire Intangible Assets Purchases of intangible assets Payments to Acquire Businesses, Net of Cash Acquired Acquisition, net of cash acquired Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] CASH FLOWS FROM FINANCING ACTIVITIES: Proceeds from Issuance Initial Public Offering Proceeds from Initial Public Offering, net of underwriting discounts Proceeds from Issuance of Common Stock Proceeds from Follow-On Public Offering, net of underwriting discounts Payments of Stock Issuance Costs Payments of costs related to public offerings Proceeds from Issuance of Convertible Preferred Stock Net proceeds from issuance of convertible preferred stock The cash inflow associated with the amount received from holders exercising their vested stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. Proceeds from Stock Options Exercised, Vested Proceeds from exercises of vested options The cash inflow associated with the amount received from holders exercising their nonvested stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. Proceeds from Stock Options Exercised, Nonvested Proceeds from exercises of nonvested options Proceeds from Stock Plans Proceeds from shares issued in ESPP Payments Related to Tax Withholding for Share-based Compensation Value of equity awards withheld for tax liabilities Payments for Repurchase of Equity Repurchases of common and preferred stock Repurchases of stock Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Effect of Exchange Rate on Cash and Cash Equivalents Effect of exchange rate changes on cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS Income Taxes Paid Cash paid for income taxes Noncash Investing and Financing Items [Abstract] NON-CASH INVESTING AND FINANCING ACTIVITIES: Purchases of property, equipment and intangible assets, accrued but not paid. Purchases of Property, Equipment and Intangible Assets, Accrued but Not Paid Purchases of property, equipment and intangible assets, accrued but not paid Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Stock-based compensation capitalized in software development costs Vesting of early exercised options. Vesting of Early Exercised Options Vesting of early exercised options Goodwill, Purchase Accounting Adjustments Business combination measurement period adjustments Measurement period adjustment Stock Issued Series T convertible preferred stock issued as part of purchase price in the Authy acquisition Costs related to public offerings, accrued but not paid. Stock Offering Costs, Accrued but Not yet Paid Costs related to public offerings, accrued but not paid Organization and Description of Business Nature of Operations [Text Block] Organization and Description of Business Summary of Significant Accounting Policies Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Summary of Significant Accounting Policies Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Property and Equipment Business Combinations Business Combination Disclosure [Text Block] Business Combinations Goodwill and Intangible Assets Goodwill and Intangible Assets Disclosure [Text Block] Goodwill and Intangible Assets Accrued Expenses and Other Liabilities The entire disclosure for accrued expenses and other liabilities. Accrued Liabilities and Other Liabilities Disclosure [Text Block] Accrued Expenses and Other Liabilities Supplemental Balance Sheet Information Schedule of Valuation and Qualifying Accounts Disclosure [Text Block] Supplemental Balance Sheet Information Revenue by Geographic Area Segment Reporting Disclosure [Text Block] Revenue by Geographic Area Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] Stockholders' Equity Stock-Based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Compensation Net Loss Per Share Attributable to Common Stockholders