Fair Value Measurements Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]

The following table summarizes the levels of fair value measurements of our financial assets:

	September 30, 2021						December 31, 2020
(in thousands)	Total		Level 1		Level 2		Total		Level 1		Level 2
Money market funds	$	454,477	$	454,477	$	—	$	551,213	$	551,213	$	—
U.S. Treasury bills	11,074		11,074		—		10,531		10,531		—
Municipal bonds	21,623		—		21,623		23,998		—		23,998
Total	$	487,174	$	465,551	$	21,623	$	585,742	$	561,744	$	23,998

Investments Classified by Contractual Maturity Date [Table Text Block]

As of September 30, 2021, the contractual maturities of our marketable securities were as follows:

(in thousands)	Amortized Cost		Estimated Fair Value
Less than one year	$	31,573	$	31,566
One to five years	1,132		1,131
Total	$	32,705	$	32,697

Debt Securities, Available-for-sale

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
September 30, 2021
U.S. Treasury bills	$	11,074	$	—	$	—	$	11,074
Municipal bonds	21,631		—		(8)		21,623
Total	$	32,705	$	—	$	(8)	$	32,697
December 31, 2020
U.S. Treasury bills	$	10,530	$	1	$	—	$	10,531
Municipal bonds	23,994		8		(4)		23,998
Total	$	34,524	$	9	$	(4)	$	34,529