Cash, Cash Equivalents and Investments - Securities Classified as Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	$ 75,288	$ 91,032
Cash and cash equivalents, Fair Value	75,288	91,032
Short-term investments
Short-term investments, Amortized Cost	66,360	95,455
Short-term investments, Gross Unrealized Gains	6	7
Short-term investments, Gross Unrealized Losses	(3)	(10)
Short-term investments, Fair Value	66,363	95,452
Long-term investments:
Total cash equivalents and investments, Amortized Cost	141,648	188,602
Total cash equivalents and investments, Gross Unrealized Gains	6	7
Total cash equivalents and investments, Gross Unrealized Losses	(3)	(11)
Total cash equivalents and investments, Fair Value	141,651	188,598
Cash
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	5,712	781
Cash and cash equivalents, Fair Value	5,712	781
Money market funds
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	68,326	88,151
Cash and cash equivalents, Fair Value	68,326	88,151
Commercial paper
Cash and cash equivalents:
Cash and cash equivalents, Amortized Cost	1,250	2,100
Cash and cash equivalents, Fair Value	1,250	2,100
Commercial paper
Short-term investments
Short-term investments, Amortized Cost	49,919	60,631
Short-term investments, Gross Unrealized Gains	3	2
Short-term investments, Gross Unrealized Losses	0	(4)
Short-term investments, Fair Value	49,922	60,629
Corporate bonds
Short-term investments
Short-term investments, Amortized Cost	11,100	24,547
Short-term investments, Gross Unrealized Gains	3	3
Short-term investments, Gross Unrealized Losses	(2)	(6)
Short-term investments, Fair Value	11,101	24,544
Long-term investments:
Long-term investments, Amortized Cost		2,115
Long-term investments, Gross Unrealized Gains
Long-term investments, Gross Unrealized Losses		(1)
Long-term investments, Fair Value		2,114
U.S. government-sponsored agency bonds
Short-term investments
Short-term investments, Amortized Cost		9,277
Short-term investments, Gross Unrealized Gains		2
Short-term investments, Gross Unrealized Losses		0
Short-term investments, Fair Value		9,279
Asset-backed securities
Short-term investments
Short-term investments, Amortized Cost	5,341
Short-term investments, Gross Unrealized Gains	0
Short-term investments, Gross Unrealized Losses	(1)
Short-term investments, Fair Value	$ 5,340
U.S. treasury notes
Short-term investments
Short-term investments, Amortized Cost		1,000
Short-term investments, Gross Unrealized Gains		0
Short-term investments, Gross Unrealized Losses		0
Short-term investments, Fair Value		$ 1,000