Debt Securities

9 Months Ended

Sep. 30, 2022

Investments, Debt and Equity Securities [Abstract]

The following table presents the amortized cost, unrealized gain and loss recognized in accumulated other comprehensive income (loss) and fair value of debt securities available-for-sale, aggregated by major security type and contractual maturity.


		September 30, 2022								December 31, 2021
(in millions)	Contractual Maturity	Amortized Cost		Unrealized Gain		Unrealized Loss		Fair Value		Amortized Cost		Unrealized Gain		Unrealized Loss		Fair Value
Commercial paper	0 to 1 years	$	97.9	$	—	$	(0.4)	$	97.5	$	204.8	$	—	$	—	$	204.8
Corporate debt securities	0 to 1 years	260.5		—		(3.2)		257.3		128.2		—		(0.1)		128.1
Securities of government-sponsored entities	0 to 1 years	237.2		—		(4.8)		232.4		37.6		—		—		37.6
		$	595.6	$	—	$	(8.4)	$	587.2	$	370.6	$	—	$	(0.1)	$	370.5

Corporate debt securities	1 to 3 years	$	270.8	$	—	$	(6.2)	$	264.6	$	358.9	$	—	$	(1.5)	$	357.4
Securities of government-sponsored entities	1 to 3 years	102.3		—		(4.3)		98.0		204.3		—		(1.0)		203.3
		$	373.1	$	—	$	(10.5)	$	362.6	$	563.2	$	—	$	(2.5)	$	560.7

As of September 30, 2022, our security portfolio consisted of 193 debt securities available-for-sale, including 183 such securities that were in an unrealized loss position but of high credit quality. Unrealized losses on these investments were primarily due to changes in interest rates. We do not intend to sell these investments and it is not more likely than not that we will be required to sell these investments before recovery of their amortized cost basis. No allowance for credit losses was recognized as of September 30, 2022 or December 31, 2021.

The following table presents debt securities available-for-sale that were in an unrealized loss position as of September 30, 2022, aggregated by major security type and length of time in a continuous loss position.


	Less Than 12 Months				12 Months or Longer				Total
(in millions)	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Commercial paper	$	52.9	$	(0.4)	$	—	$	—	$	52.9	$	(0.4)
Corporate debt securities	$	251.1	$	(4.8)	$	263.7	$	(4.6)	$	514.8	$	(9.4)
Securities of government-sponsored entities	$	235.0	$	(6.0)	$	92.9	$	(3.1)	$	327.9	$	(9.1)

The following table presents debt securities available-for-sale that were in an unrealized loss position as of December 31, 2021, aggregated by major security type and length of time in a continuous loss position.


	Less Than 12 Months				12 Months or Longer				Total
(in millions)	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate debt securities	$	428.6	$	(1.6)	$	—	$	—	$	428.6	$	(1.6)
Securities of government-sponsored entities	$	230.5	$	(1.0)	$	—	$	—	$	230.5	$	(1.0)

Accrued interest receivables on debt securities available-for-sale totaled $3.9 million and $2.2 million, respectively, as of September 30, 2022 and December 31, 2021. We do not measure an allowance for credit losses for accrued interest receivables. For the purposes of identifying and measuring an impairment, accrued interest is excluded from both the fair value and amortized cost basis of the debt security. Uncollectible accrued interest receivables associated with an impaired debt security are reversed against interest income upon identification of the impairment. No accrued interest receivables were written off during the nine months ended September 30, 2022 or 2021.