Debt Securities (Tables)

12 Months Ended

Dec. 31, 2021

Investments, Debt and Equity Securities [Abstract]

Amortized cost, gross unrealized gain (loss) positions and estimated fair value for available-for-sale debt securities

The following table summarizes the amortized cost, unrealized gain and loss recognized in accumulated other comprehensive income (loss) and fair value of debt securities available-for-sale at December 31, 2021, aggregated by major security type and contractual maturity:


		December 31, 2021								December 31, 2020
(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	$	204.8	$	—	$	—	$	204.8	$	82.2	$	—	$	—	$	82.2
Corporate debt securities	0 to 1 years	128.2		—		(0.1)		128.1		299.3		1.4		—		300.7
Securities of government-sponsored entities	0 to 1 years	37.6		—		—		37.6		230.9		0.1		—		231.0
		$	370.6	$	—	$	(0.1)	$	370.5	$	612.4	$	1.5	$	—	$	613.9

Corporate debt securities	1 to 3 years	$	358.9	$	—	$	(1.5)	$	357.4	$	144.8	$	0.4	$	—	$	145.2
Securities of government-sponsored entities	1 to 3 years	204.3		—		(1.0)		203.3		81.9		0.1		(0.1)		81.9
		$	563.2	$	—	$	(2.5)	$	560.7	$	226.7	$	0.5	$	(0.1)	$	227.1

Gross unrealized losses and fair value available-for-sale investments in unrealized loss position

The following table summarizes debt securities available-for-sale in an unrealized loss position for less than 12 months, aggregated by major security type. There were no debt securities available-for-sale in an unrealized loss position for longer than 12 months as of December 31, 2021 or 2020.


	December 31, 2021				December 31, 2020
(in millions)	Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate Debt Securities	$	428.6	$	(1.6)	$	—	$	—
Securities of government-sponsored entities	230.5		(1.0)		95.0		(0.1)
	$	659.1	$	(2.6)	$	95.0	$	(0.1)