Investments (Tables)

12 Months Ended

Dec. 31, 2014

Notes to Financial Statements [Abstract]

Schedule of Available-for-sale Securities Reconciliation

At December 31, 2014 and 2013, all fixed maturity securities were classified as available-for-sale. In the following charts, prior year amounts have been reclassified, where applicable, between public utilities and all other corporate bonds to conform to the current year categorization of certain securities.

The amortized cost and fair values of securities by security type are shown as follows.

	December 31, 2014
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	983.5	$	255.5	$	0.5	$	1,238.5
States, Municipalities, and Political Subdivisions	1,745.0		377.6		1.1		2,121.5
Foreign Governments	1,101.1		206.3		—		1,307.4
Public Utilities	7,046.1		1,505.4		0.9		8,550.6
Mortgage/Asset-Backed Securities	2,224.9		207.0		0.1		2,431.8
All Other Corporate Bonds	25,658.8		3,828.6		122.2		29,365.2
Redeemable Preferred Stocks	44.0		5.9		—		49.9
Total Fixed Maturity Securities	$	38,803.4	$	6,386.3	$	124.8	$	45,064.9

	December 31, 2013
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	1,028.6	$	173.1	$	5.6	$	1,196.1
States, Municipalities, and Political Subdivisions	1,706.0		117.2		40.0		1,783.2
Foreign Governments	1,226.4		149.6		2.8		1,373.2
Public Utilities	7,121.7		901.2		25.7		7,997.2
Mortgage/Asset-Backed Securities	1,858.7		184.6		4.0		2,039.3
All Other Corporate Bonds	25,315.2		2,828.3		225.8		27,917.7
Redeemable Preferred Stocks	33.0		4.7		—		37.7
Total Fixed Maturity Securities	$	38,289.6	$	4,358.7	$	303.9	$	42,344.4

Length of Time Fixed Maturity Securities had been in a Gross Unrealized Loss Position

The following charts indicate the length of time our fixed maturity securities have been in a gross unrealized loss position.

	December 31, 2014
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	—	$	—	$	7.4	$	0.5
States, Municipalities, and Political Subdivisions	1.6		—		42.0		1.1
Public Utilities	5.1		0.2		58.2		0.7
Mortgage/Asset-Backed Securities	28.0		—		1.9		0.1
All Other Corporate Bonds	1,666.2		82.2		729.4		40.0
Total Fixed Maturity Securities	$	1,700.9	$	82.4	$	838.9	$	42.4

	December 31, 2013
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
	(in millions of dollars)
United States Government and Government Agencies and Authorities	$	41.1	$	3.1	$	5.2	$	2.5
States, Municipalities, and Political Subdivisions	412.5		33.5		37.2		6.5
Foreign Governments	87.2		2.8		—		—
Public Utilities	506.0		23.7		27.5		2.0
Mortgage/Asset-Backed Securities	341.0		3.6		2.5		0.4
All Other Corporate Bonds	3,776.9		197.4		238.6		28.4
Total Fixed Maturity Securities	$	5,164.7	$	264.1	$	311.0	$	39.8

Distribution of the Maturity Dates for Fixed Maturity Securities

The following is a distribution of the maturity dates for fixed maturity securities. The maturity dates have not been adjusted for possible calls or prepayments.

	December 31, 2014
	Total Amortized Cost		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
	(in millions of dollars)
1 year or less	$	1,372.0	$	34.3	$	1,406.3	$	—	$	—
Over 1 year through 5 years	6,871.2		719.3		7,434.0		9.4		147.1
Over 5 years through 10 years	9,532.9		1,003.3		8,792.3		80.9		1,663.0
Over 10 years	18,802.4		4,422.4		22,490.6		34.4		699.8
	36,578.5		6,179.3		40,123.2		124.7		2,509.9
Mortgage/Asset-Backed Securities	2,224.9		207.0		2,401.9		0.1		29.9
Total Fixed Maturity Securities	$	38,803.4	$	6,386.3	$	42,525.1	$	124.8	$	2,539.8

	December 31, 2013
	Total Amortized Cost		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
	(in millions of dollars)
1 year or less	$	903.9	$	20.6	$	915.5	$	—	$	9.0
Over 1 year through 5 years	7,098.2		727.1		7,678.5		0.6		146.2
Over 5 years through 10 years	9,492.6		940.2		8,137.4		95.8		2,199.6
Over 10 years	18,936.2		2,486.2		18,441.5		203.5		2,777.4
	36,430.9		4,174.1		35,172.9		299.9		5,132.2
Mortgage/Asset-Backed Securities	1,858.7		184.6		1,695.8		4.0		343.5
Total Fixed Maturity Securities	$	38,289.6	$	4,358.7	$	36,868.7	$	303.9	$	5,475.7

Mortgage Loans by Property Type and Geographic Region

Mortgage loans by property type and geographic region are presented below.

	December 31
	2014				2013
	(in millions of dollars)
	Carrying		Percent of		Carrying		Percent of
	Amount		Total		Amount		Total
Property Type
Apartment	$	110.1	5.9	%	$	61.1	3.3	%
Industrial	542.9		29.2		567.8		31.3
Office	794.0		42.8		776.5		42.8
Retail	409.6		22.1		409.7		22.6
Total	$	1,856.6	100.0	%	$	1,815.1	100.0	%

Region
New England	$	105.6	5.7	%	$	100.9	5.6	%
Mid-Atlantic	179.4		9.7		191.5		10.5
East North Central	210.6		11.4		244.3		13.5
West North Central	166.2		8.9		162.3		8.9
South Atlantic	453.6		24.4		447.7		24.7
East South Central	75.3		4.1		67.7		3.7
West South Central	215.6		11.6		190.9		10.5
Mountain	116.0		6.2		101.9		5.6
Pacific	334.3		18.0		307.9		17.0
Total	$	1,856.6	100.0	%	$	1,815.1	100.0	%

Mortgage Loans by Credit Quality Indicators

Mortgage loans, sorted by the applicable credit quality indicators, are as follows:

	December 31
	2014		2013
	(in millions of dollars)
Internal Rating
Aa	$	7.7	$	10.8
A	666.0		683.1
Baa	1,156.7		1,094.6
Ba	13.1		13.5
B	13.1		13.1
Total	$	1,856.6	$	1,815.1

Loan-to-Value Ratio
<= 65%	$	898.7	$	777.4
> 65% <= 75%	818.0		867.5
> 75% <= 85%	102.3		107.6
> 85%	37.6		62.6
Total	$	1,856.6	$	1,815.1

Troubled Debt Restructurings on Financing Receivables

A summary of our troubled debt restructurings is as follows:

	Year Ended December 31
	2014		2013		2012
	(in millions of dollars)
Foreclosure
Carrying Amount	$	18.1	$	4.3	$	17.3
Number of Loans	1		1		3

Activity in the Allowance for Credit Losses

The activity in the allowance for credit losses is as follows:

	Year Ended December 31
	2014			2013		2012
	(in millions of dollars)
Balance at Beginning of Year	$	1.5		$	1.5	$	1.5
Provision	3.0			—		1.8
Charge-offs, Net of Recoveries	(3.0		)	—		(1.8		)
Balance at End of Year	$	1.5		$	1.5	$	1.5

Schedule of Financial Instrument and Derivative Offsetting

Shown below are our financial instruments that either meet the accounting requirements that allow them to be offset in our balance sheets or that are subject to an enforceable master netting arrangement or similar agreement. Our accounting policy is to not offset these financial instruments in our balance sheets. Net amounts disclosed below have been reduced by the amount of collateral pledged to or received from our counterparties.

	December 31, 2014
	Gross Amount						Gross Amount Not
	of Recognized		Gross Amount		Net Amount		Offset in Balance Sheet
	Financial		Offset in		Presented in		Financial			Cash			Net
	Instruments		Balance Sheet		Balance Sheet		Instruments			Collateral			Amount
	(in millions of dollars)
Financial Assets:
Derivatives	$	28.0	$	—	$	28.0	$	(7.2	)	$	(15.4	)	$	5.4
Securities Lending	176.5		—		176.5		(118.1		)	(58.4		)	—
Total	$	204.5	$	—	$	204.5	$	(125.3	)	$	(73.8	)	$	5.4
Financial Liabilities:
Derivatives	$	92.9	$	—	$	92.9	$	(67.0	)	$	—		$	25.9
Securities Lending	58.4		—		58.4		(58.4		)	—			—
Total	$	151.3	$	—	$	151.3	$	(125.4	)	$	—		$	25.9

	December 31, 2013
	Gross Amount						Gross Amount Not
	of Recognized		Gross Amount		Net Amount		Offset in Balance Sheet
	Financial		Offset in		Presented in		Financial			Cash			Net
	Instruments		Balance Sheet		Balance Sheet		Instruments			Collateral			Amount
	(in millions of dollars)
Financial Assets:
Derivatives	$	10.8	$	—	$	10.8	$	(9.5	)	$	(1.1	)	$	0.2
Securities Lending	201.6		—		201.6		(125.1		)	(76.5		)	—
Total	$	212.4	$	—	$	212.4	$	(134.6	)	$	(77.6	)	$	0.2
Financial Liabilities:
Derivatives	$	135.6	$	—	$	135.6	$	(98.6	)	$	—		$	37.0
Securities Lending	76.5		—		76.5		(76.5		)	—			—
Total	$	212.1	$	—	$	212.1	$	(175.1	)	$	—		$	37.0

Investment Income

Net Investment Income

Net investment income reported in our consolidated statements of income is as follows:

	Year Ended December 31
	2014		2013		2012
	(in millions of dollars)
Fixed Maturity Securities	$	2,344.4	$	2,371.6	$	2,404.0
Derivatives	40.4		35.2		28.9
Mortgage Loans	109.8		109.2		107.1
Policy Loans	16.3		15.7		14.8
Other Long-term Investments	23.0		18.0		15.2
Short-term Investments	2.4		2.4		4.3
Gross Investment Income	2,536.3		2,552.1		2,574.3
Less Investment Expenses	29.0		29.5		26.9
Less Investment Income on Participation Fund Account Assets	15.1		15.7		16.1
Less Amortization of Tax Credit Partnerships	14.8		14.8		16.1
Net Investment Income	$	2,477.4	$	2,492.1	$	2,515.2

Realized Investment Gains and Losses Reported in Consolidated Statements of Income

Realized Investment Gain and Loss

Realized investment gains and losses are as follows:

	Year Ended December 31
	2014			2013			2012
	(in millions of dollars)
Fixed Maturity Securities
Gross Gains on Sales	$	9.3		$	15.8		$	29.3
Gross Losses on Sales	(7.5		)	(45.7		)	(20.4		)
Other-Than-Temporary Impairment Loss	(13.5		)	(0.8		)	—
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	21.2			15.6			5.0
Gross Losses on Sales	(0.8		)	—			(4.3		)
Impairment Loss	(3.4		)	(2.0		)	(1.9		)
Embedded Derivative in Modified Coinsurance Arrangement	3.3			30.7			51.8
All Other Derivatives	11.0			(1.9		)	—
Foreign Currency Transactions	(3.5		)	(4.9		)	(3.3		)
Net Realized Investment Gain	$	16.1		$	6.8		$	56.2