Investments (Tables)

3 Months Ended

Mar. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Held-To-Maturity Investments

The amortized cost, unrealized gains and losses, and fair value of our held-to-maturity investments at March 31, 2021 and December 31, 2020 are summarized as follows:

			Fair Value Measurements as of March 31, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(in thousands)
Held-to-maturity investments
Commercial paper	$	116,658	$	—	$	(24)	$	116,634
State and municipal bonds	15,805		—		(21)		15,784
Corporate bonds and notes	164,847		—		(644)		164,203
Total held-to-maturity investments	$	297,310	$	—	$	(689)	$	296,621

			Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
	(in thousands)
Held-to-maturity investments
Treasury securities	$	149,996	$	—	$	(1)	$	149,995
Commercial paper	37,963		—		(15)		37,948
Corporate bonds and notes	49,892		—		(63)		49,829
Total held-to-maturity investments	$	237,851	$	—	$	(79)	$	237,772

	March 31, 2021				December 31, 2020
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
	(in thousands)				(in thousands)
Due in one year or less	$	144,829	$	144,788	$	201,881	$	201,864
Due after one year through five years	152,481		151,833		35,970		35,908
Total held-to-maturity securities	$	297,310	$	296,621	$	237,851	$	237,772