Investment (Tables)

9 Months Ended

Sep. 30, 2015

Investments [Abstract]

Amortized Costs and Fair Values of Fixed Maturity Securities Available-for-Sale

		September 30, 2015
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In millions)
Corporate bonds		$	7,014.1	$	292.7	$	(88.9)	$	7,217.9
U.S. government and agency bonds			201.6		31.5		---		233.1
U.S. state and political subdivision bonds			139.8		10.0		(0.1)		149.7
Foreign government bonds			79.8		6.4		---		86.2
Mortgage/asset-backed bonds			264.3		4.0		(2.0)		266.3
	Total fixed maturity securities	$	7,699.6	$	344.6	$	(91.0)	$	7,953.2

		December 31, 2014
		Amortized		Unrealized		Unrealized		Fair
		Cost		Gains		Losses		Value
		(In millions)
Corporate bonds		$	6,740.6	$	366.5	$	(37.0)	$	7,070.1
U.S. government and agency bonds			223.2		35.6		(0.2)		258.6
U.S. state and political subdivision bonds			125.8		10.4		(0.1)		136.1
Foreign government bonds			58.4		6.5		---		64.9
Mortgage/asset-backed bonds			242.0		4.1		(2.1)		244.0
	Total fixed maturity securities	$	7,390.0	$	423.1	$	(39.4)	$	7,773.7

Schedule of Contractual Maturities of Fixed Maturity Securities Available-for-Sale

		September 30, 2015				December 31, 2014
		Amortized		Fair		Amortized		Fair
		Cost		Value		Cost		Value
		(In millions)
Due in one year or less		$	628.7	$	636.7	$	649.0	$	658.0
Due after one year through five years			2,895.9		3,017.3		3,060.8		3,215.4
Due after five years through ten years			3,034.4		3,050.9		2,847.9		2,916.7
Due after ten years			1,140.6		1,248.3		832.3		983.6
	Total fixed maturity securities	$	7,699.6	$	7,953.2	$	7,390.0	$	7,773.7

Schedule of Gross Unrealized Losses and Fair Value of Investments

				September 30, 2015
				Total				Less than 12 months				12 or more months
				Number		Amount		Number		Amount		Number		Amount
				(Dollars in millions)
Unrealized losses:
		Corporate bonds			1,273	$	88.9		1,079	$	62.8		194	$	26.1
		U.S. state and political subdivision bonds			2		0.1		2		0.1		---		---
		Mortgage/asset-backed bonds			35		2.0		27		1.3		8		0.7
			Total		1,310	$	91.0		1,108	$	64.2		202	$	26.8
Fair market value of securities with
	unrealized losses:
		Corporate bonds			1,273	$	2,146.6		1,079	$	1,874.7		194	$	271.9
		U.S. state and political subdivision bonds			2		6.2		2		6.2		---		---
		Mortgage/asset-backed bonds			35		105.9		27		82.6		8		23.3
			Total		1,310	$	2,258.7		1,108	$	1,963.5		202	$	295.2

				December 31, 2014
				Total				Less than 12 months				12 or more months
				Number		Amount		Number		Amount		Number		Amount
				(Dollars in millions)
Unrealized losses:
		Corporate bonds			956	$	37.0		653	$	19.9		303	$	17.1
		U.S. government and agency bonds			5		0.2		---		---		5		0.2
		U.S. state and political subdivision bonds			4		0.1		---		---		4		0.1
		Mortgage/asset-backed bonds			39		2.1		30		1.4		9		0.7
			Total		1,004	$	39.4		683	$	21.3		321	$	18.1
Fair market value of securities with
	unrealized losses:
		Corporate bonds			956	$	1,646.0		653	$	1,074.9		303	$	571.1
		U.S. government and agency bonds			5		6.4		---		---		5		6.4
		U.S. state and political subdivision bonds			4		6.9		---		---		4		6.9
		Mortgage/asset-backed bonds			39		117.2		30		87.3		9		29.9
			Total		1,004	$	1,776.5		683	$	1,162.2		321	$	614.3

Commercial Mortgage Loan Portfolio by Property Type, by Geographic Region within the U.S. and by U.S. State

			September 30, 2015				December 31, 2014
			Amount		Percent		Amount		Percent
			(Dollars in millions)
Property type:
	Retail		$	2,714.2	48.9	%	$	2,627.1	49.4	%
	Office			1,059.3	19.1			1,013.4	19.1
	Industrial			1,041.4	18.8			1,001.5	18.8
	Commercial			211.0	3.8			213.6	4.0
	Hotel/motel			204.5	3.7			165.7	3.1
	Apartment and other			316.9	5.7			299.8	5.6
		Total commercial mortgage loans, net	$	5,547.3	100.0	%	$	5,321.1	100.0	%
Geographic region*:
	Pacific		$	1,977.1	35.6	%	$	1,914.6	36.0	%
	South Atlantic			1,093.4	19.7			1,065.5	20.0
	West South Central			730.6	13.2			676.9	12.7
	Mountain			644.8	11.6			606.5	11.4
	East North Central			487.4	8.8			466.0	8.8
	Middle Atlantic			243.1	4.4			215.3	4.0
	East South Central			195.3	3.5			188.7	3.6
	West North Central			131.3	2.4			140.1	2.6
	New England			44.3	0.8			47.5	0.9
		Total commercial mortgage loans, net	$	5,547.3	100.0	%	$	5,321.1	100.0	%
U.S. state:
	California		$	1,455.5	26.2	%	$	1,434.2	27.0	%
	Texas			682.3	12.3			623.4	11.7
	Florida			323.3	5.8			309.4	5.8
	Georgia			301.3	5.4			306.6	5.8
	Other states			2,784.9	50.3			2,647.5	49.7
		Total commercial mortgage loans, net	$	5,547.3	100.0	%	$	5,321.1	100.0	%

Changes in Commercial Mortgage Loan Loss Allowance

				Three Months Ended				Nine Months Ended
				September 30,				September 30,
				2015		2014		2015		2014
				(In millions)
Commercial mortgage loan loss allowance:
	Beginning balance			$	35.5	$	44.4	$	40.0	$	43.6
		Provision change (gain) loss			(1.9)		5.9		(4.1)		8.1
		Charge-offs			(0.3)		(8.8)		(2.6)		(10.2)
			Ending balance	$	33.3	$	41.5	$	33.3	$	41.5
	Specific loan loss allowance			$	23.3	$	24.6	$	23.3	$	24.6
	General loan loss allowance				10.0		16.9		10.0		16.9
			Total commercial mortgage loan loss allowance	$	33.3	$	41.5	$	33.3	$	41.5

Schedule of Recorded Investment in Commercial Mortgage Loans

		September 30,		December 31,
		2015		2014
		(In millions)
Commercial mortgage loans collectively evaluated for impairment		$	5,484.1	$	5,255.2
Commercial mortgage loans individually evaluated for impairment			96.5		105.9
Commercial mortgage loan loss allowance			(33.3)		(40.0)
	Total commercial mortgage loans, net	$	5,547.3	$	5,321.1

Performing and Nonperforming Commercial Mortgage Loans by Property Type

		September 30, 2015
										Hotel/		Apartment
		Retail		Office		Industrial		Commercial		Motel		and Other		Total
		(In millions)
Performing commercial mortgage loans		$	2,713.7	$	1,059.3	$	1,040.9	$	211.0	$	204.5	$	316.9	$	5,546.3
Nonperforming commercial mortgage loans			0.5		---		0.5		---		---		---		1.0
	Total commercial mortgage loans	$	2,714.2	$	1,059.3	$	1,041.4	$	211.0	$	204.5	$	316.9	$	5,547.3

		December 31, 2014
										Hotel/		Apartment
		Retail		Office		Industrial		Commercial		Motel		and Other		Total
		(In millions)
Performing commercial mortgage loans		$	2,622.4	$	1,012.7	$	1,001.4	$	213.6	$	165.7	$	299.1	$	5,314.9
Nonperforming commercial mortgage loans			4.7		0.7		0.1		---		---		0.7		6.2
	Total commercial mortgage loans	$	2,627.1	$	1,013.4	$	1,001.5	$	213.6	$	165.7	$	299.8	$	5,321.1

Impaired Commercial Mortgage Loans Identified in Management's Specific Review of Probable Loan Losses and the Related Allowance

						September 30, 2015
								Unpaid				Amount on
						Recorded		Principal		Related		Nonaccrual
						Investment		Balance		Allowance		Status
						(In millions)
Impaired commercial mortgage loans:
	Without specific loan loss allowance:
		Retail				$	21.5	$	21.5	$	---	$	0.3
		Industrial					0.9		0.9		---		---
		Commercial					0.5		0.5		---		---
		Office					0.1		0.1		---		---
			Total impaired commercial mortgage loans without specific
				loan loss allowance			23.0		23.0		---		0.3
	With specific loan loss allowance:
		Retail					53.0		53.0		12.8		1.2
		Commercial					8.4		8.4		6.8		0.5
		Office					7.6		7.6		1.7		---
		Industrial					4.5		4.5		2.0		0.4
			Total impaired commercial mortgage loans with specific
				loan loss allowance			73.5		73.5		23.3		2.1
					Total impaired commercial mortgage loans	$	96.5	$	96.5	$	23.3	$	2.4

						December 31, 2014
								Unpaid				Amount on
						Recorded		Principal		Related		Nonaccrual
						Investment		Balance		Allowance		Status
						(In millions)
Impaired commercial mortgage loans:
	Without specific loan loss allowance:
		Retail				$	25.0	$	25.0	$	---	$	10.5
		Office					1.6		1.6		---		---
		Commercial					2.3		2.3		---		0.5
		Apartment and other					2.8		2.8		---		---
			Total impaired commercial mortgage loans without specific
				loan loss allowance			31.7		31.7		---		11.0
	With specific loan loss allowance:
		Retail					52.2		52.2		12.3		7.7
		Office					8.6		8.6		2.9		---
		Industrial					4.6		4.6		1.6		0.1
		Commercial					8.5		8.5		7.0		0.6
		Apartment and other					0.3		0.3		---		---
			Total impaired commercial mortgage loans with specific
				loan loss allowance			74.2		74.2		23.8		8.4
					Total impaired commercial mortgage loans	$	105.9	$	105.9	$	23.8	$	19.4

Troubled Debt Restructurings on Financing Receivables [Table Text Block]

			Three Months Ended September 30, 2015						Nine Months Ended September 30, 2015
					Pre-		Post-				Pre-		Post-
					Restructuring		Restructuring				Restructuring		Restructuring
			Number		Recorded		Recorded		Number		Recorded		Recorded
			of Loans		Investment		Investment		of Loans		Investment		Investment
			(Dollars in millions)
Troubled debt restructurings:
	Retail			---	$	---	$	---		3	$	1.5	$	1.5
	Office			---		---		---		2		1.1		1.2
		Total troubled debt restructurings		---	$	---	$	---		5	$	2.6	$	2.7

			Three Months Ended September 30, 2014						Nine Months Ended September 30, 2014
					Pre-		Post-				Pre-		Post-
					Restructuring		Restructuring				Restructuring		Restructuring
			Number		Recorded		Recorded		Number		Recorded		Recorded
			of Loans		Investment		Investment		of Loans		Investment		Investment
			(Dollars in millions)
Troubled debt restructurings:
	Retail			33	$	27.5	$	24.9		34	$	28.3	$	25.6
	Office			1		0.7		0.7		1		0.7		0.7
	Industrial			1		0.4		0.4		3		2.1		2.3
	Commercial			---		---		---		1		2.7		2.7
		Total troubled debt restructurings		35	$	28.6	$	26.0		39	$	33.8	$	31.3

Average Recorded Investment in Impaired Commercial Mortgage Loans before Specific Allowances for Losses

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2015		2014		2015		2014
	(In millions)
Average recorded investment	$	97.5	$	100.5	$	99.8	$	105.5

Aging of Commercial Mortgage Loans by Property Type

			September 30, 2015
															Total
							Greater Than				Allowance				Commercial
			30 Days		60 Days		90 Days		Total		Related		Current,		Mortgage
			Past Due		Past Due		Past Due		Past Due		to Past Due		Net		Loans
			(In millions)
Commercial mortgage loans:
	Retail		$	1.3	$	---	$	2.4	$	3.7	$	(1.9)	$	2,712.4	$	2,714.2
	Office			---		---		---		---		---		1,059.3		1,059.3
	Industrial			0.6		---		0.7		1.3		(0.3)		1,040.4		1,041.4
	Commercial			---		---		---		---		---		211.0		211.0
	Hotel/motel			---		---		---		---		---		204.5		204.5
	Apartment and other			---		---		---		---		---		316.9		316.9
		Total commercial mortgage loans	$	1.9	$	---	$	3.1	$	5.0	$	(2.2)	$	5,544.5	$	5,547.3

			December 31, 2014
															Total
							Greater Than				Allowance				Commercial
			30 Days		60 Days		90 Days		Total		Related		Current,		Mortgage
			Past Due		Past Due		Past Due		Past Due		to Past Due		Net		Loans
			(In millions)
Commercial mortgage loans:
	Retail		$	0.2	$	2.0	$	4.8	$	7.0	$	(2.1)	$	2,622.2	$	2,627.1
	Office			1.9		---		0.8		2.7		---		1,010.7		1,013.4
	Industrial			0.5		---		0.3		0.8		(0.2)		1,000.9		1,001.5
	Commercial			---		---		---		---		---		213.6		213.6
	Hotel/motel			---		---		---		---		---		165.7		165.7
	Apartment and other			0.2		0.7		---		0.9		---		298.9		299.8
		Total commercial mortgage loans	$	2.8	$	2.7	$	5.9	$	11.4	$	(2.3)	$	5,312.0	$	5,321.1

Net Investment Income Summarized by Investment Type

			Three Months Ended				Nine Months Ended
			September 30,				September 30,
			2015		2014		2015		2014
			(In millions)
Fixed maturity securities			$	77.4	$	73.4	$	229.4	$	221.0
Commercial mortgage loans				84.6		83.1		249.3		250.1
Real estate				0.8		0.5		2.3		0.7
S&P 500 Index options				(5.4)		0.9		(3.8)		5.3
Other				0.6		---		0.9		4.4
	Gross investment income			158.0		157.9		478.1		481.5
Investment expenses				(4.7)		(4.5)		(13.5)		(17.9)
Tax-advantaged investments				0.4		(0.8)		1.7		(2.3)
		Net investment income	$	153.7	$	152.6	$	466.3	$	461.3

Schedule of Gross Capital Gains and Losses by Investment Type

				Three Months Ended				Nine Months Ended
				September 30,				September 30,
				2015		2014		2015		2014
				(In millions)
Gains:
	Fixed maturity securities			$	0.8	$	1.4	$	5.2	$	4.8
	Commercial mortgage loans				2.4		0.8		4.8		1.8
	Real estate				0.2		0.8		0.2		1.9
	Other				---		0.3		---		0.3
		Gross capital gains			3.4		3.3		10.2		8.8
Losses:
	Fixed maturity securities				(5.5)		(0.4)		(8.5)		(1.5)
	Provision for commercial mortgage loan losses				---		(5.9)		---		(8.1)
	Real estate				(1.1)		(1.7)		(2.4)		(3.4)
	Other (1)				(3.0)		---		(14.6)		(1.1)
		Gross capital losses			(9.6)		(8.0)		(25.5)		(14.1)
			Net capital losses	$	(6.2)	$	(4.7)	$	(15.3)	$	(5.3)