Investments (Tables)

6 Months Ended

Jun. 30, 2020

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, 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	$	286.8	$	—	$	286.8	$	20.1	$	—	$	306.9
Foreign government		4.2		—		4.2		0.5		—		4.7
Municipal		918.2		—		918.2		50.4		0.3		968.3
Corporate		3,775.2		3.8		3,771.4		293.3		3.7		4,061.0
Residential mortgage-backed		922.3		—		922.3		42.2		—		964.5
Commercial mortgage-backed		659.2		—		659.2		47.2		0.3		706.1
Asset-backed		65.4		—		65.4		2.1		—		67.5
Total fixed maturities	$	6,631.3	$	3.8	$	6,627.5	$	455.8	$	4.3	$	7,079.0

	December 31, 2019
			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
(in millions)	Cost		Gains		Losses		Fair Value		Losses
U.S. Treasury and government agencies	$	342.0	$	9.1	$	1.3	$	349.8	$	—
Foreign government		15.7		0.4		—		16.1		—
Municipal		807.1		27.6		1.2		833.5		—
Corporate		3,653.5		161.6		3.9		3,811.2		3.0
Residential mortgage-backed		905.4		17.1		1.1		921.4		—
Commercial mortgage-backed		666.4		25.6		0.1		691.9		—
Asset-backed		62.1		1.1		—		63.2		—
Total fixed maturities	$	6,452.2	$	242.5	$	7.6	$	6,687.1	$	3.0

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, 2020
	Amortized Cost, net
	of Allowance for		Fair
(in millions)	Credit Losses		Value
Due in one year or less	$	345.6	$	350.2
Due after one year through five years		1,902.4		2,023.9
Due after five years through ten years		2,228.8		2,432.1
Due after ten years		503.8		534.7
		4,980.6		5,340.9
Mortgage-backed and asset-backed securities		1,646.9		1,738.1
Total fixed maturities	$	6,627.5	$	7,079.0

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, 2020 and December 31, 2019 including the length of time the securities have been in an unrealized loss position:

	June 30, 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	$	—	$	0.5	$	—	$	—	$	—	$	0.5
Municipal		0.3		17.0		—		—		0.3		17.0
Corporate		0.6		41.6		—		—		0.6		41.6
Residential mortgage-backed		—		14.1		—		0.5		—		14.6
Commercial mortgage-backed		0.3		30.3		—		—		0.3		30.3
Asset-backed		—		1.4		—		—		—		1.4
Total investment grade		1.2		104.9		—		0.5		1.2		105.4
Below investment grade:
Corporate		3.1		90.4		—		—		3.1		90.4
Total fixed maturities	$	4.3	$	195.3	$	—	$	0.5	$	4.3	$	195.8

	December 31, 2019
	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	$	1.3	$	73.0	$	—	$	9.3	$	1.3	$	82.3
Municipal		1.1		72.5		0.1		5.6		1.2		78.1
Corporate		0.7		86.5		0.1		4.7		0.8		91.2
Residential mortgage-backed		0.7		69.2		0.4		34.4		1.1		103.6
Commercial mortgage-backed		0.1		40.6		—		0.9		0.1		41.5
Asset-backed		—		—		—		1.7		—		1.7
Total investment grade		3.9		341.8		0.6		56.6		4.5		398.4
Below investment grade:
Corporate		2.2		27.1		0.9		9.0		3.1		36.1
Total fixed maturities	$	6.1	$	368.9	$	1.5	$	65.6	$	7.6	$	434.5

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,
	2020						2019
	Proceeds from		Gross		Gross		Proceeds from		Gross		Gross
(in millions)	Sales		Gains		Losses		Sales		Gains		Losses
Fixed maturities	$	91.5	$	2.3	$	2.3	$	162.5	$	1.6	$	1.1

	Six Months Ended June 30,
	2020						2019
	Proceeds from		Gross		Gross		Proceeds from		Gross		Gross
(in millions)	Sales		Gains		Losses		Sales		Gains		Losses
Fixed maturities, excluding held-for-sale (Chaucer)	$	157.5	$	5.0	$	2.7	$	222.6	$	2.6	$	2.6
Fixed maturities, held-for-sale		—		—		—		0.3		—		—
Total fixed maturities	$	157.5	$	5.0	$	2.7	$	222.9	$	2.6	$	2.6

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

	Three Months Ended June 30,					Six Months Ended June 30,
(in millions)		2020			2019		2020			2019
Net gains (losses) recognized during the period	$	61.5		$	11.7	$	(74.7	)	$	60.3
Less: net (losses) gains recognized on equity securities sold    during the period		(15.8	)		0.1		(16.4	)		1.2
Net unrealized gains (losses) recognized during the period on equity    securities still held	$	77.3		$	11.6	$	(58.3	)	$	59.1