Fair Value Measurements Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Marketable Securities [Table Text Block]

Fair Value of Instruments Measured and Recognized at Fair Value

The following tables summarize the levels of fair value measurements of our financial assets:

	December 31, 2021						December 31, 2020
(in thousands)	Total		Level 1		Level 2		Total		Level 1		Level 2
Money market funds	$	579,105	$	579,105	$	—	$	551,213	$	551,213	$	—
U.S. Treasury bills	5,782		5,782		—		10,531		10,531		—
Municipal bonds	26,009		—		26,009		23,998		—		23,998
Total	$	610,896	$	584,887	$	26,009	$	585,742	$	561,744	$	23,998

Available-for-sale Securities [Table Text Block]

The following is a summary of our available-for-sale marketable securities:

(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Estimated Fair Value
December 31, 2021
U.S. Treasury bills	$	5,783	$	—	$	(1)	$	5,782
Municipal bonds	26,017		—		(8)		26,009
December 31, 2020
U.S. Treasury bills	$	10,530	$	1	$	—	$	10,531
Municipal bonds	23,994		8		(4)		23,998