Cash and Investments - Schedule of Securities Classified as Cash and Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Cash and cash equivalents, Amortized Cost	$ 91,032	$ 181,133	$ 78,768	$ 75,383
Cash and cash equivalents, Amortized Cost		181,130
Cash and cash equivalents, Gross Unrealized Gains		3
Cash and cash equivalents, Fair Value	91,032	181,133
Short-term investments, Amortized Cost	95,455	66,362
Short-term investments, Gross Unrealized Gains	7	20
Short-term investments, Gross Unrealized Losses	(10)	(3)
Short-term investments, Fair Value	95,452	66,379
Cash equivalents and short-term investments, Amortized Cost		247,492
Cash equivalents and investments, Amortized Cost	188,602
Cash equivalents and short-term investments, Gross Unrealized Gains		23
Cash equivalents and short-term investments, Gross Unrealized Losses		(3)
Cash equivalents and short-term investments, Fair Value		247,512
Cash equivalents and investments, Gross Unrealized Gains	7
Cash equivalents and investments, Gross Unrealized Losses	(11)
Cash equivalents and investments, Fair Value	188,598
Money Market Funds [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Cash and cash equivalents, Amortized Cost	88,151	147,208
Cash and cash equivalents, Fair Value	88,151	147,208
Commercial Paper (Cash Equivalents) [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Cash and cash equivalents, Fair Value		19,360
Short-term investments, Amortized Cost	2,100	19,357
Short-term investments, Gross Unrealized Gains		3
Short-term investments, Fair Value	2,100
Corporate Bonds (Investments) [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Cash and cash equivalents, Fair Value		11,441
Short-term investments, Amortized Cost		11,441
Cash [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Cash and cash equivalents, Amortized Cost	781	3,124
Cash and cash equivalents, Fair Value	781	3,124
Commercial Paper (Investments) [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Short-term investments, Amortized Cost	60,631	21,690
Short-term investments, Gross Unrealized Gains	2	6
Short-term investments, Gross Unrealized Losses	(4)	(3)
Short-term investments, Fair Value	60,629	21,693
Corporate Bonds (Investments) [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Short-term investments, Amortized Cost	24,547	36,667
Short-term investments, Gross Unrealized Gains	3	14
Short-term investments, Gross Unrealized Losses	(6)
Short-term investments, Fair Value	24,544	36,681
Long-term investments, Amortized Cost	2,115
Long-term investments, Gross Unrealized Losses	(1)
Long-term Investments, Fair Value	2,114
U.S. Government-Sponsored Agency Bonds [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Short-term investments, Amortized Cost	9,277
Short-term investments, Gross Unrealized Gains	2
Short-term investments, Fair Value	9,279
Asset-Backed Securities [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Short-term investments, Amortized Cost		8,005
Short-term investments, Fair Value		$ 8,005
U.S. Treasury Notes [Member]
Cash Cash Equivalents, Short Term Investments And Long-Term Investments [Line Items]
Short-term investments, Amortized Cost	1,000
Short-term investments, Fair Value	$ 1,000