Cash Equivalents and Marketable Securities - Summary of Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	$ 336,374	$ 363,052
Unrealized Gains, Total	490	151
Unrealized Losses, Total	(336)	(52)
Fair Value, Total	336,528	363,151
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	54,841	34,851
Unrealized Gains, Total	0	1
Unrealized Losses, Total	0	(1)
Fair Value, Total	54,841	34,851
Cash Equivalents | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total		10,205
Unrealized Gains, Total		0
Unrealized Losses, Total		(1)
Fair Value, Total		10,204
Cash Equivalents | Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	54,841	17,664
Unrealized Gains, Total	0	0
Unrealized Losses, Total	0	0
Fair Value, Total	54,841	17,664
Cash Equivalents | Corporate Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total		6,982
Unrealized Gains, Total		1
Unrealized Losses, Total		0
Fair Value, Total		6,983
Short-term marketable securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	251,933	275,970
Unrealized Gains, Total	416	124
Unrealized Losses, Total	(307)	(51)
Fair Value, Total	252,042	276,043
Short-term marketable securities | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	142,848	154,678
Unrealized Gains, Total	99	54
Unrealized Losses, Total	(307)	(42)
Fair Value, Total	142,640	154,690
Short-term marketable securities | Corporate Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	93,091	95,061
Unrealized Gains, Total	256	36
Unrealized Losses, Total	0	(9)
Fair Value, Total	93,347	95,088
Short-term marketable securities | Government- sponsored Enterprise Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	15,994	26,231
Unrealized Gains, Total	61	34
Unrealized Losses, Total	0	0
Fair Value, Total	16,055	26,265
Long-term marketable securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	29,600	52,231
Unrealized Gains, Total	74	26
Unrealized Losses, Total	(29)	0
Fair Value, Total	29,645	52,257
Long-term marketable securities | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	8,563	14,194
Unrealized Gains, Total	0	8
Unrealized Losses, Total	(29)	0
Fair Value, Total	8,534	14,202
Long-term marketable securities | Government- sponsored Enterprise Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost, Total	21,037	38,037
Unrealized Gains, Total	74	18
Unrealized Losses, Total	0	0
Fair Value, Total	$ 21,111	$ 38,055