Fair Value Measurements - Fair Value by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	$ 104,711	$ 27,041
Over One Year Through Five Years	93,852	40,505
Over Five Years	0	0
Total	198,563	67,546
U.S. Treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	22,550	6,075
Over One Year Through Five Years	30,114	15,265
Over Five Years	0	0
Total	52,664	21,340
Yankee bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	4,150
Over One Year Through Five Years	2,010
Over Five Years	0
Total	6,160
Agency bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	14,041
Over One Year Through Five Years	3,489
Over Five Years	0
Total	17,530
Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	0
Over One Year Through Five Years	12,229
Over Five Years	0
Total	12,229
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	17,690	14,543
Over One Year Through Five Years	0	0
Over Five Years	0	0
Total	17,690	14,543
Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	20,868	560
Over One Year Through Five Years	6,667	13,978
Over Five Years	0	0
Total	27,535	14,538
Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
One Year or Less	25,412	5,863
Over One Year Through Five Years	39,343	11,262
Over Five Years	0	0
Total	$ 64,755	$ 17,125