Fair Value Measurements Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2020

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, 2020						December 31, 2019
(in thousands)	Total		Level 1		Level 2		Total		Level 1		Level 2
Money market funds	$	353,819	$	353,819	$	—	$	363,075	$	363,075	$	—
U.S. Treasury bills	10,411		10,411		—		34,728		34,728		—
Municipal bonds	23,583		—		23,583		—		—		—
Total	$	387,813	$	364,230	$	23,583	$	397,803	$	397,803	$	—

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
September 30, 2020
U.S. Treasury bills	$	10,410	$	1	$	—	$	10,411
Municipal bonds	23,554		29		—		23,583
Total	$	33,964	$	30	$	—	$	33,994
December 31, 2019
U.S. Treasury bills	$	34,716	$	13	$	(1)	$	34,728
Total	$	34,716	$	13	$	(1)	$	34,728

Investments Classified by Contractual Maturity Date [Table Text Block]

As of September 30, 2020, the contractual maturities of our marketable securities were as follows:

(in thousands)	Amortized Cost		Estimated Fair Value
Less than one year	$	33,964	$	33,994
One to five years	—		—
Total	$	33,964	$	33,994