Investments (Tables)

3 Months Ended

Mar. 31, 2019

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:

	March 31, 2019
			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
(in millions)	Cost		Gains		Losses		Fair Value		Losses
U.S. Treasury and government agencies	$	404.5	$	4.7	$	2.5	$	406.7	$	—
Foreign government		7.3		0.1		—		7.4		—
Municipal		848.1		20.8		3.4		865.5		—
Corporate		3,635.7		66.3		27.4		3,674.6		4.8
Residential mortgage-backed		819.2		6.8		6.1		819.9		—
Commercial mortgage-backed		684.9		9.4		2.4		691.9		—
Asset-backed		93.0		0.6		0.2		93.4		—
Total fixed maturities	$	6,492.7	$	108.7	$	42.0	$	6,559.4	$	4.8

	December 31, 2018
			Gross		Gross				OTTI
	Amortized		Unrealized		Unrealized				Unrealized
(in millions)	Cost		Gains		Losses		Fair Value		Losses
U.S. Treasury and government agencies	$	414.7	$	2.4	$	7.2	$	409.9	$	—
Foreign government		7.3		0.1		—		7.4		—
Municipal		879.0		16.6		9.8		885.8		—
Corporate		3,476.6		26.1		92.0		3,410.7		6.6
Residential mortgage-backed		728.4		2.7		14.7		716.4		—
Commercial mortgage-backed		648.4		1.7		9.8		640.3		—
Asset-backed		91.5		0.2		0.7		91.0		—
Fixed maturities, excluding held-for-sale (Chaucer)		6,245.9		49.8		134.2		6,161.5		6.6
Fixed maturities, held-for-sale		24.9		—		0.4		24.5		—
Total fixed maturities	$	6,270.8	$	49.8	$	134.6	$	6,186.0	$	6.6

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.

	March 31, 2019
	Amortized		Fair
(in millions)	Cost		Value
Due in one year or less	$	249.2	$	250.9
Due after one year through five years		1,969.6		2,001.6
Due after five years through ten years		2,407.4		2,423.2
Due after ten years		269.4		278.5
		4,895.6		4,954.2
Mortgage-backed and asset-backed securities		1,597.1		1,605.2
Total fixed maturities	$	6,492.7	$	6,559.4

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 March 31, 2019 and December 31, 2018 including the length of time the securities have been in an unrealized loss position:

	March 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	$	—	$	—	$	2.5	$	158.4	$	2.5	$	158.4
Foreign governments		—		—		—		0.8		—		0.8
Municipal		—		9.7		3.4		192.3		3.4		202.0
Corporate		0.9		15.3		19.7		993.2		20.6		1,008.5
Residential mortgage-backed		—		2.1		6.1		352.6		6.1		354.7
Commercial mortgage-backed		—		0.3		2.4		226.7		2.4		227.0
Asset-backed		—		—		0.2		31.9		0.2		31.9
Total investment grade		0.9		27.4		34.3		1,955.9		35.2		1,983.3
Below investment grade:
Corporate		0.3		17.1		6.5		75.7		6.8		92.8
Total fixed maturities	$	1.2	$	44.5	$	40.8	$	2,031.6	$	42.0	$	2,076.1

	December 31, 2018
	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	$	1.1	$	66.0	$	6.1	$	210.9	$	7.2	$	276.9
Foreign governments		—		2.0		—		0.8		—		2.8
Municipal		0.8		110.0		9.0		248.0		9.8		358.0
Corporate		30.0		1,277.9		43.9		781.6		73.9		2,059.5
Residential mortgage-backed		2.6		201.2		12.1		323.7		14.7		524.9
Commercial mortgage-backed		3.4		293.0		6.4		175.5		9.8		468.5
Asset-backed		0.4		42.3		0.3		18.0		0.7		60.3
Total investment grade		38.3		1,992.4		77.8		1,758.5		116.1		3,750.9
Below investment grade:
Municipal		—		—		—		0.9		—		0.9
Corporate		8.1		185.6		10.0		54.0		18.1		239.6
Total below investment grade		8.1		185.6		10.0		54.9		18.1		240.5
Fixed maturities, excluding held-for-sale (Chaucer)		46.4		2,178.0		87.8		1,813.4		134.2		3,991.4
Fixed maturities, held-for-sale		0.1		4.0		0.3		18.0		0.4		22.0
Total fixed maturities	$	46.5	$	2,182.0	$	88.1	$	1,831.4	$	134.6	$	4,013.4

Schedule of Realized Gain (Loss)

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

	Three Months Ended March 31,
	2019						2018
	Proceeds from		Gross		Gross		Proceeds from		Gross		Gross
(in millions)	Sales		Gains		Losses		Sales		Gains		Losses
Fixed maturities, excluding held-for-sale (Chaucer)	$	60.1	$	1.0	$	1.5	$	57.1	$	0.2	$	1.7
Fixed maturities, held-for-sale		0.3		—		—		70.7		0.4		0.6
Total fixed maturities	$	60.4	$	1.0	$	1.5	$	127.8	$	0.6	$	2.3

Rollforward of Cumulative Amounts Related to Credit Loss Portion of OTTI Losses

The following table provides rollforwards of the cumulative amounts related to the Company’s credit loss portion of the OTTI losses on fixed maturity securities from continuing operations for which the non-credit portion of the loss is included in other comprehensive income. 

	Three Months Ended March 31,
(in millions)	2019			2018
Credit losses as of the beginning of the period	$	3.8		$	3.6
Credit losses on securities for which an OTTI was not previously recognized		—			0.2
Reductions for securities sold, matured or called		(0.5	)		(0.7	)
Credit losses as of the end of the period	$	3.3		$	3.1

Schedule of Pre-tax Realized and Unrealized Gains and Losses on Equity Securities From Continuing Operations

	Three Months Ended March 31,
(in millions)		2019		2018
Net gains (losses) recognized during the period	$	48.6	$	(22.9	)
Less: net gains recognized on equity securities sold during the period		1.1		0.5
Net unrealized gains (losses) recognized during the period on equity securities still held	$	47.5	$	(23.4	)