Investments (Tables)

12 Months Ended

Dec. 31, 2011

Notes to Financial Statements [Abstract]

Schedule of Available-for-sale Securities Reconciliation

At December 31, 2011 and 2010, all fixed maturity securities were classified as available-for-sale. The amortized cost and fair values of securities by security type are shown as follows.

	December 31, 2011
	(in millions of dollars)
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
United States Government and Government Agencies and Authorities	$	1,005.8	$	299.7	$	1.1	$	1,304.4
States, Municipalities, and Political Subdivisions	1,377.8		222.6		8.8		1,591.6
Foreign Governments	1,139.4		237.3		—		1,376.7
Public Utilities	9,015.7		1,646.2		28.6		10,633.3
Mortgage/Asset-Backed Securities	2,634.6		344.1		5.5		2,973.2
All Other Corporate Bonds	21,411.6		3,314.8		176.3		24,550.1
Redeemable Preferred Stocks	55.8		3.5		1.9		57.4
Total Fixed Maturity Securities	$	36,640.7	$	6,068.2	$	222.2	$	42,486.7

There were no other-than-temporary impairments recognized in accumulated other comprehensive income as of December 31, 2011.

	December 31, 2010
	(in millions of dollars)
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value		Other-Than- Temporary Impairments in AOCI (1)
United States Government and Government Agencies and Authorities	$	981.7	$	128.6	$	8.6	$	1,101.7	$	—
States, Municipalities, and Political Subdivisions	1,271.0		21.5		47.3		1,245.2		—
Foreign Governments	1,248.6		160.7		—		1,409.3		—
Public Utilities	8,874.2		854.3		44.3		9,684.2		—
Mortgage/Asset-Backed Securities	3,047.8		338.3		0.6		3,385.5		—
All Other Corporate Bonds	21,067.5		2,221.3		134.1		23,154.7		3.9
Redeemable Preferred Stocks	55.8		1.7		2.5		55.0		—
Total Fixed Maturity Securities	$	36,546.6	$	3,726.4	$	237.4	$	40,035.6	$	3.9

(1) Accumulated Other Comprehensive Income (Loss)

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 had been in a gross unrealized loss position.

	December 31, 2011
	(in millions of dollars)
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
United States Government and Government Agencies and Authorities	$	—	$	—	$	6.3	$	1.1
States, Municipalities, and Political Subdivisions	51.6		1.3		75.3		7.5
Public Utilities	192.0		7.9		142.2		20.7
Mortgage/Asset-Backed Securities	94.2		4.8		19.6		0.7
All Other Corporate Bonds	1,703.9		65.5		684.9		110.8
Redeemable Preferred Stocks	—		—		20.9		1.9
Total Fixed Maturity Securities	$	2,041.7	$	79.5	$	949.2	$	142.7

	December 31, 2010
	(in millions of dollars)
	Less Than 12 Months				12 Months or Greater
	Fair Value		Gross Unrealized Loss		Fair Value		Gross Unrealized Loss
United States Government and Government Agencies and Authorities	$	23.9	$	3.1	$	10.9	$	5.5
States, Municipalities, and Political Subdivisions	660.6		28.4		100.3		18.9
Public Utilities	1,073.8		41.0		41.0		3.3
Mortgage/Asset-Backed Securities	34.5		0.1		45.5		0.5
All Other Corporate Bonds	1,667.2		48.3		1,071.7		85.8
Redeemable Preferred Stocks	7.6		0.4		20.7		2.1
Total Fixed Maturity Securities	$	3,467.6	$	121.3	$	1,290.1	$	116.1

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, 2011
	(in millions of dollars)
	Total Amortized Cost		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
1 year or less	$	715.1	$	16.0	$	701.4	$	0.1	$	29.6
Over 1 year through 5 years	5,161.5		449.8		4,949.0		20.7		641.6
Over 5 years through 10 years	9,630.5		1,266.3		9,903.8		52.8		940.2
Over 10 years	18,499.0		3,992.0		21,082.2		143.1		1,265.7
	34,006.1		5,724.1		36,636.4		216.7		2,877.1
Mortgage/Asset-Backed Securities	2,634.6		344.1		2,859.4		5.5		113.8
Total Fixed Maturity Securities	$	36,640.7	$	6,068.2	$	39,495.8	$	222.2	$	2,990.9

	December 31, 2010
	(in millions of dollars)
	Total Amortized Cost		Unrealized Gain Position				Unrealized Loss Position
			Gross Gain		Fair Value		Gross Loss		Fair Value
1 year or less	$	685.7	$	10.9	$	532.6	$	0.4	$	163.6
Over 1 year through 5 years	4,740.6		394.1		4,886.3		5.5		242.9
Over 5 years through 10 years	9,501.6		931.6		9,415.0		37.1		981.1
Over 10 years	18,570.9		2,051.5		17,138.5		193.8		3,290.1
	33,498.8		3,388.1		31,972.4		236.8		4,677.7
Mortgage/Asset-Backed Securities	3,047.8		338.3		3,305.5		0.6		80.0
Total Fixed Maturity Securities	$	36,546.6	$	3,726.4	$	35,277.9	$	237.4	$	4,757.7

Credit Losses Remaining in Retained Earnings Related to Adoption of Accounting Standard

The following table presents the before-tax credit related portion of other-than-temporary impairments on fixed maturity securities still held as of the dates shown for which a portion of the other-than-temporary impairment was recognized in other comprehensive income.

	Year Ended December 31
	2011			2010			2009
	(in millions of dollars)
Balance at Beginning of Year	$	8.5		$	18.3		$	—
Credit Losses Remaining in Retained Earnings Related to the Adoption of Accounting Standard	—			—			30.8
Impairment Recognized on Securities not Previously Impaired	—			—			38.4
Additional Impairment Recognized on Securities Previously Impaired	—			—			4.4
Sales or Maturities of Securities	(8.5		)	(9.8		)	(38.3		)
Reduction for Credit Loss Impairments Previously Recognized due to Change in Intent to Sell	—			—			(17.0		)
Balance at End of Year	$	—		$	8.5		$	18.3

Mortgage Loans by Property Type

Mortgage loans by property type and geographic region are as follows:

	December 31
	2011				2010
	(in millions of dollars)
	Carrying		Percent of		Carrying		Percent of
	Amount		Total		Amount		Total
Property Type
Apartment	$	28.0	1.8	%	$	33.7	2.2	%
Industrial	502.0		31.1		458.2		30.2
Mixed	93.5		5.8		95.8		6.3
Office	659.3		40.9		634.7		41.9
Retail	322.4		20.0		286.9		18.9
Other	7.1		0.4		7.5		0.5
Total	$	1,612.3	100.0	%	$	1,516.8	100.0	%

Mortgage Loans by Geographic Region

Region
New England	$	147.0	9.1	%	$	146.8	9.7	%
Mid-Atlantic	174.1		10.8		184.8		12.2
East North Central	212.7		13.2		171.7		11.3
West North Central	151.2		9.4		134.6		8.9
South Atlantic	383.8		23.8		372.0		24.5
East South Central	52.4		3.3		26.9		1.8
West South Central	160.4		9.9		171.8		11.3
Mountain	69.5		4.3		60.7		4.0
Pacific	261.2		16.2		247.5		16.3
Total	$	1,612.3	100.0	%	$	1,516.8	100.0	%

Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Internal Rating

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

	December 31
	2011		2010
	(in millions of dollars)
Internal Rating
Aa	$	10.9	$	19.0
A	712.6		744.4
Baa	855.0		732.9
Ba	20.7		20.5
B	13.1		—
Total	$	1,612.3	$	1,516.8

Mortgage Loans, Sorted by Applicable Credit Quality Indicators, Loan to Value Ratio

Loan-to-Value Ratio
<= 65%	$	578.4	$	425.3
> 65% <= 75%	802.3		869.2
> 75% <= 85%	165.1		161.9
> 85% <= 100%	66.5		60.4
Total	$	1,612.3	$	1,516.8

Activity in the Allowance for Credit Losses

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

	Year Ended December 31
	2011		2010			2009
	(in millions of dollars)
Balance at Beginning of Year	$	1.5	$	3.2		$	—
Provision	—		2.4			5.5
Charge-offs, Net of Recoveries	—		(4.1		)	(2.3		)
Balance at End of Year	$	1.5	$	1.5		$	3.2

Impaired Mortgage Loans

Impaired mortgage loans are as follows:

	December 31, 2011
	(in millions of dollars)
			Unpaid
	Recorded		Principal		Related
	Investment		Balance		Allowance
With No Related Allowance Recorded	$	9.4	$	9.4	$	—
With an Allowance Recorded	13.1		14.6		1.5
Total	$	22.5	$	24.0	$	1.5
	December 31, 2010
	(in millions of dollars)
			Unpaid
	Recorded		Principal		Related
	Investment		Balance		Allowance
With No Related Allowance Recorded	$	9.8	$	9.8	$	—
With an Allowance Recorded	13.1		14.6		1.5
Total	$	22.9	$	24.4	$	1.5

Troubled Debt Restructurings on Financing Receivables [Table Text Block]

Our troubled debt restructurings consist of loan foreclosures or the acceptance of a discounted payoff and/or sale of the loan. A summary of our troubled debt restructurings is as follows:

	Year Ended December 31
	2011		2010		2009
	(in millions of dollars)
Foreclosure
Carrying Amount	$	19.9	$	7.2	$	21.1
Number of Loans	2		1		1
Payoff/Sale
Carrying Amount	$	3.2	$	4.7	$	8.4
Realized Loss	$	0.2	$	1.4	$	2.1
Number of Loans	1		3		2

We had no realized losses on foreclosures for the years ended December 31, 2011, 2010, and 2009.

Investment Income [Table Text Block]

Net Investment Income

	Year Ended December 31
	2011		2010		2009
	(in millions of dollars)
Fixed Maturity Securities	$	2,425.2	$	2,401.9	$	2,268.5
Derivative Financial Instruments	22.9		17.2		13.5
Mortgage Loans	100.1		91.1		81.0
Policy Loans	14.1		13.9		12.4
Other Long-term Investments	13.1		18.5		11.5
Short-term Investments	2.9		3.2		6.9
Gross Investment Income	2,578.3		2,545.8		2,393.8
Less Investment Expenses	26.9		28.2		29.2
Less Investment Income on PFA Assets	17.4		18.8		18.0
Less Amortization of Tax Credit Partnerships	14.4		3.3		—
Net Investment Income	$	2,519.6	$	2,495.5	$	2,346.6

Realized Investment Gains and Losses Reported in Consolidated Statements of Income

Realized Investment Gain and Loss

Realized investment gains and losses reported in our consolidated statements of income are as follows:

	Year Ended December 31
	2011			2010			2009
	(in millions of dollars)
Fixed Maturity Securities
Gross Gains on Sales	$	74.0		$	61.1		$	48.6
Gross Losses on Sales	(24.0		)	(41.3		)	(83.5		)
Other-Than-Temporary Impairment Loss	(19.9		)	(15.9		)	(211.8		)
Mortgage Loans and Other Invested Assets
Gross Gains on Sales	7.1			7.9			10.0
Gross Losses on Sales	(0.5		)	(0.5		)	(0.4		)
Impairment Loss	(0.6		)	(3.8		)	(8.1		)
Embedded Derivative in Modified Coinsurance Arrangement	(39.4		)	21.1			243.1
Other Derivatives	—			—			12.3
Foreign Currency Transactions	(1.6		)	(3.9		)	1.5
Net Realized Investment Gain (Loss)	$	(4.9	)	$	24.7		$	11.7