Stockholders' Equity - Common Stock Shares Reserved (Details) - shares	Mar. 31, 2020	Dec. 31, 2019
Stockholders' Equity
Total (in shares)	53,009,614	46,270,890
2016 Stock Option and Incentive Plan
Stockholders' Equity
Stock-based awards available for grant under 2016 Plan (in shares)	20,998,004	14,957,734
Common Class A
Stockholders' Equity
Class A common stock reserved for Twilio.org (in shares)	773,571	795,673
Class A common stock reserved for the convertible senior notes (in shares)	10,472,165	10,472,165
Stock options issued and outstanding
Stockholders' Equity
Stock options issued and outstanding (in shares)	7,492,970	7,705,848
Nonvested restricted stock units issued and outstanding
Stockholders' Equity
Nonvested restricted stock units issued and outstanding (in shares)	8,039,823	8,490,517
Class A common stock committed under 2016 ESPP
Stockholders' Equity
Stock-based awards available for grant under 2016 Plan (in shares)	5,233,081	3,848,953