Fair Value Measurements - Schedule of Amortized Cost (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			$ 202,589,000	$ 67,590,000
Gross Unrealized Gains			5,000	1,000
Gross Unrealized Losses			(450,000)	(45,000)
Fair Value			202,144,000	67,546,000
Accrued interest receivable			500,000	200,000
Realized gains (losses) on marketable securities	$ 0	$ 0
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			52,039,000	21,357,000
Gross Unrealized Gains			1,000	1,000
Gross Unrealized Losses			(97,000)	(18,000)
Fair Value			51,943,000	21,340,000
Yankee bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			3,062,000
Gross Unrealized Gains			0
Gross Unrealized Losses			(4,000)
Fair Value			3,058,000
Agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			17,594,000
Gross Unrealized Gains			0
Gross Unrealized Losses			(4,000)
Fair Value			17,590,000
Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			12,478,000
Gross Unrealized Gains			0
Gross Unrealized Losses			(67,000)
Fair Value			12,411,000
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			21,964,000	14,543,000
Gross Unrealized Gains			0	0
Gross Unrealized Losses			0	0
Fair Value			21,964,000	14,543,000
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			26,630,000	14,546,000
Gross Unrealized Gains			0	0
Gross Unrealized Losses			(26,000)	(8,000)
Fair Value			26,604,000	14,538,000
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost			68,822,000	17,144,000
Gross Unrealized Gains			4,000	0
Gross Unrealized Losses			(252,000)	(19,000)
Fair Value			$ 68,574,000	$ 17,125,000