Fair Value Measurements - Schedule of Fair Value and Amortized Cost of Investments in Marketable Securities by Major Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 157,578	$ 188,270
Unrealized Gain	315	67
Unrealized Loss	(27)	(3)
Fair Value	157,866	188,334
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	67,326	45,498
Fair Value	67,326	45,498
Corporate Securities and Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	34,589	67,918
Unrealized Gain	9	55
Unrealized Loss	(27)	(2)
Fair Value	34,571	67,971
U.S. Government Treasury and Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	55,663	74,854
Unrealized Gain	306	12
Unrealized Loss		(1)
Fair Value	$ 55,969	$ 74,865