Investments (Tables)

6 Months Ended

Jun. 30, 2021

Investments Debt And Equity Securities [Abstract]

Schedule of Available-for-sale Fixed Maturities Reconciliation

The amortized cost and fair value of available-for-sale fixed maturities were as follows:

	June 30, 2021
						Amortized Cost,
			Allowance			Net of Allowance		Gross		Gross
	Amortized		for Credit			for Credit		Unrealized		Unrealized
(in millions)	Cost		Losses			Losses		Gains		Losses		Fair Value
U.S. Treasury and government agencies	$	381.5	$	—		$	381.5	$	12.1	$	6.7	$	386.9
Foreign government		2.2		—			2.2		0.4		—		2.6
Municipal		1,053.9		—			1,053.9		45.3		2.0		1,097.2
Corporate		3,965.5		(0.1	)		3,965.4		256.2		8.2		4,213.4
Residential mortgage-backed		980.0		—			980.0		22.0		4.2		997.8
Commercial mortgage-backed		739.3		—			739.3		41.8		1.5		779.6
Asset-backed		75.7		—			75.7		2.6		—		78.3
Total fixed maturities	$	7,198.1	$	(0.1	)	$	7,198.0	$	380.4	$	22.6	$	7,555.8

	December 31, 2020
						Amortized Cost,
			Allowance			Net of Allowance		Gross		Gross
	Amortized		for Credit			for Credit		Unrealized		Unrealized
(in millions)	Cost		Losses			Losses		Gains		Losses		Fair Value
U.S. Treasury and government agencies	$	376.4	$	—		$	376.4	$	17.6	$	2.0	$	392.0
Foreign government		2.2		—			2.2		0.5		—		2.7
Municipal		1,042.1		—			1,042.1		61.7		0.1		1,103.7
Corporate		3,770.0		(0.1	)		3,769.9		341.8		0.4		4,111.3
Residential mortgage-backed		978.2		—			978.2		33.1		0.6		1,010.7
Commercial mortgage-backed		705.4		—			705.4		54.8		0.2		760.0
Asset-backed		71.4		—			71.4		2.6		—		74.0
Total fixed maturities	$	6,945.7	$	(0.1	)	$	6,945.6	$	512.1	$	3.3	$	7,454.4

Investments Classified by Contractual Maturity Date

The amortized cost and fair value by maturity periods for fixed maturities are shown in the following table. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties, or the Company may have the right to put or sell the obligations back to the issuers.

	June 30, 2021
	Amortized Cost, Net
	of Allowance for		Fair
(in millions)	Credit Losses		Value
Due in one year or less	$	268.9	$	272.7
Due after one year through five years		1,907.3		2,040.1
Due after five years through ten years		2,491.1		2,639.1
Due after ten years		735.7		748.2
		5,403.0		5,700.1
Mortgage-backed and asset-backed securities		1,795.0		1,855.7
Total fixed maturities	$	7,198.0	$	7,555.8

Schedule of Unrealized Loss on Investments

The following tables provide information about the Company’s available-for-sale fixed maturity securities that were in an unrealized loss position at June 30, 2021 and December 31, 2020, including the length of time the securities have been in an unrealized loss position:

	June 30, 2021
	12 months or less				Greater than 12 months				Total
	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
(in millions)	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	6.7	$	185.4	$	—	$	—	$	6.7	$	185.4
Municipal		2.0		176.1		—		0.5		2.0		176.6
Corporate		7.2		298.4		—		—		7.2		298.4
Residential mortgage-backed		4.2		304.5		—		—		4.2		304.5
Commercial mortgage-backed		1.5		72.3		—		—		1.5		72.3
Total investment grade		21.6		1,036.7		—		0.5		21.6		1,037.2
Below investment grade:
Corporate		1.0		42.0		—		—		1.0		42.0
Total fixed maturities	$	22.6	$	1,078.7	$	—	$	0.5	$	22.6	$	1,079.2

	December 31, 2020
	12 months or less				Greater than 12 months				Total
	Gross				Gross				Gross
	Unrealized		Fair		Unrealized		Fair		Unrealized		Fair
(in millions)	Losses		Value		Losses		Value		Losses		Value
Investment grade:
U.S. Treasury and government agencies	$	2.0	$	140.7	$	—	$	—	$	2.0	$	140.7
Municipal		0.1		19.3		—		0.7		0.1		20.0
Corporate		0.4		53.4		—		—		0.4		53.4
Residential mortgage-backed		0.6		94.4		—		—		0.6		94.4
Commercial mortgage-backed		0.2		33.2		—		—		0.2		33.2
Total investment grade		3.3		341.0		—		0.7		3.3		341.7
Below investment grade:
Corporate		—		4.6		—		—		—		4.6
Total fixed maturities	$	3.3	$	345.6	$	—	$	0.7	$	3.3	$	346.3

Schedule of Realized Gain (Loss)

The proceeds from sales of available-for-sale fixed maturities and gross realized gains and gross realized losses on those sales were as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
(in millions)
Proceeds from sales	$	34.7	$	91.5	$	252.1	$	157.5
Gross gains		1.0		2.3		3.9		5.0
Gross losses		0.2		2.3		7.4		2.7

Schedule of Pre-tax Net Realized and Unrealized Gains (Losses) on Equity Securities

The following table provides pre-tax net realized and unrealized gains (losses) on equity securities:

	Three Months Ended June 30,						Six Months Ended June 30,
(in millions)		2021			2020			2021		2020
Net gains (losses) recognized during the period	$	26.5		$	61.5		$	65.6	$	(74.7	)
Less: net (losses) gains recognized on equity securities sold    during the period		(0.1	)		(15.8	)		0.5		(16.4	)
Net unrealized gains (losses) recognized during the period on equity    securities still held	$	26.6		$	77.3		$	65.1	$	(58.3	)