Investments (Amortized Costs And Fair Values Of Fixed Maturity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Total fixed maturity securities-available-for-sale, Amortized Cost	$ 6,418.5	$ 6,209.9
Total fixed maturity securities-available-for-sale, Unrealized Gains	704.7	580.5
Total fixed maturity securities-available-for-sale, Unrealized losses	(2.8)	(20.9)
Total fixed maturity securities-available-for-sale	7,120.4	6,769.5
Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	7,120.4	6,769.5
U.S. Government and Agency Bonds [Member]
Total fixed maturity securities-available-for-sale, Amortized Cost	365.6	387.8
Total fixed maturity securities-available-for-sale, Unrealized Gains	64.7	64.3
Total fixed maturity securities-available-for-sale, Unrealized losses	0	0
U.S. Government and Agency Bonds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	430.3	452.1
U.S. State and Political Subdivision Bonds [Member]
Total fixed maturity securities-available-for-sale, Amortized Cost	158.7	164.8
Total fixed maturity securities-available-for-sale, Unrealized Gains	17.8	14.0
Total fixed maturity securities-available-for-sale, Unrealized losses	0	0
U.S. State and Political Subdivision Bonds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	176.5	178.8
Foreign Government Bonds [Member]
Total fixed maturity securities-available-for-sale, Amortized Cost	61.4	61.7
Total fixed maturity securities-available-for-sale, Unrealized Gains	10.9	10.4
Total fixed maturity securities-available-for-sale, Unrealized losses	0	0
Foreign Government Bonds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	72.3	72.1
Corporate Bonds [Member]
Total fixed maturity securities-available-for-sale, Amortized Cost	5,819.0	5,588.4
Total fixed maturity securities-available-for-sale, Unrealized Gains	611.3	491.8
Total fixed maturity securities-available-for-sale, Unrealized losses	(2.8)	(20.9)
Corporate Bonds [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	6,427.5	6,059.3
S and P Five Hundred Index Options [Member]
Total fixed maturity securities-available-for-sale, Amortized Cost	13.8	7.2
Total fixed maturity securities-available-for-sale, Unrealized Gains	0	0
Total fixed maturity securities-available-for-sale, Unrealized losses	0	0
S and P Five Hundred Index Options [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	$ 13.8	$ 7.2

Amount of available-for-sale debt securities at cost, net of adjustments, which include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section 25

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-Name Accounting Standards Codification

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Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details