Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Measurements

Summary of financial assets and liabilities measured on recurring basis

	December 31, 2020								December 31, 2019
	Level I		Level II		Level III		Total		Level I		Level II		Level III		Total
	(in thousands)
Financial Assets:
Money market deposits	$	28,990		—	$	—	$	28,990	$	22,477	$	—	$	—	$	22,477
U.S. Treasury securities		597,744		—		—		597,744		293,157		—		—		293,157
Corporate bonds and notes		—		12,328		—		12,328		—		—		—		—
Municipal securities		—		78,534		—		78,534		—		85,908		—		85,908
Total financial assets	$	626,734	$	90,862	$	—	$	717,596	$	315,634	$	85,908	$	—	$	401,542