Investments

12 Months Ended

Dec. 31, 2021

Investments

Investments

4. Investments

The fair values of the Company’s investments are based upon prices provided by an independent pricing service. Management has assessed and concluded that these prices are reasonable and has not adjusted any prices received from the independent provider.

The amortized cost, gross unrealized gains and losses, fair value of those investments classified as available-for-sale, and allowance for credit losses at December 31, 2021 are summarized as follows (in thousands):

	December 31, 2021
	Amortized		Gross		Gross		Fair		Allowance for
	Cost		Unrealized Gains		Unrealized Losses		Value		Credit Losses
Corporate bonds	$	228,614	$	—		(2,232)		226,382		—
U.S. Treasuries		1,014,319		20		(456)		1,013,883		—
Total	$	1,242,933	$	20	$	(2,688)	$	1,240,265	$	—

The aggregate fair value of available-for-sale securities in an unrealized loss position at December 31, 2021 was $969.0 million. No available-for-sale securities have been in a continuous unrealized loss position for greater than 12 months.

The cost, gross unrealized gains and losses, and fair value of those investments classified as equity securities at December 31, 2021 are summarized as follows (in thousands):

	December 31, 2021
			Gross		Gross		Fair
		Cost	Unrealized Gains		Unrealized Losses		Value
Fixed income mutual funds	$	70,247	$	—	$	(574)	$	69,673
Exchange traded mutual funds		71,010		7,312		—		78,322
Total	$	141,257	$	7,312	$	(574)	$	147,995

A summary of the amortized cost and fair value of investments classified as available-for-sale, by contractual maturity, as of December 31, is as follows (in thousands):

	December 31, 2021
		Amortized	Fair
Maturity:		Cost	Value
Within one year	$	670,584	$	670,306
After one through five years		572,349		569,959
Total	$	1,242,933	$	1,240,265

Accrued interest income was $3.7 million and zero at December 31, 2021 and December 31, 2020, respectively, and is included within the balance for prepaid expenses and other current assets in the consolidated balance sheets.