Fair Value Measurements - Marketable Debt Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost	$ 109,331	$ 117,970	$ 87,016
Gross Unrealized Gains	5,219	7,043	3,695
Gross Unrealized Losses	(154)	(1)	0
Estimated Fair Value	114,396	125,012	90,711
Other-than-temporary Impairments	0	0	0
Municipal bonds — available-for-sale
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Amortized Cost	109,331	117,970	87,016
Gross Unrealized Gains	5,219	7,043	3,695
Gross Unrealized Losses	(154)	(1)	0
Estimated Fair Value	114,396	125,012	90,711
Other-than-temporary Impairments	$ 0	$ 0	$ 0