Investments (Tables)

9 Months Ended

Sep. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Held-To-Maturity Investments

The amortized cost, unrealized gains and losses, and fair value, and maturities of our held-to-maturity investments at September 30, 2021 and December 31, 2020 are summarized as follows:

			Fair Value Measurements as of September 30, 2021
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Commercial paper	$	93,452	$	8	$	(7)	$	93,453
State and municipal bonds	17,798		5		(4)		17,799
Corporate bonds and notes	188,196		24		(278)		187,942
Total held-to-maturity investments	$	299,446	$	37	$	(289)	$	299,194

			Fair Value Measurements as of December 31, 2020
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
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

	September 30, 2021				December 31, 2020
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	144,465	$	144,461	$	201,881	$	201,864
Due after one year through five years	154,981		154,733		35,970		35,908
Total held-to-maturity investments	$	299,446	$	299,194	$	237,851	$	237,772