Investments (Amortized Costs And Fair Values Of Fixed Maturity Securities Available-For-Sale) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost	$ 7,390.0	$ 6,811.9
Total fixed maturity securities-available-for-sale, Unrealized Gains	423.1	385.8
Total fixed maturity securities-available-for-sale, Unrealized Losses	(39.4)	(77.2)
Total fixed maturity securities-available-for-sale	7,773.7	7,120.5
Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale	7,773.7	7,120.5
U S Government Agencies Debt Securities [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost	262.0	320.8
Total fixed maturity securities-available-for-sale, Unrealized Gains	38.3	32.8
Total fixed maturity securities-available-for-sale, Unrealized Losses	(0.2)	(0.4)
Total fixed maturity securities-available-for-sale	300.1	353.2
U S Government Agencies Debt Securities [Member] \| Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale	300.1	353.2
U S States And Political Subdivisions [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost	125.8	134.3
Total fixed maturity securities-available-for-sale, Unrealized Gains	10.4	6.8
Total fixed maturity securities-available-for-sale, Unrealized Losses	(0.1)	(0.8)
Total fixed maturity securities-available-for-sale	136.1	140.3
U S States And Political Subdivisions [Member] \| Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale	136.1	140.3
Foreign Government Debt [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost	58.4	58.9
Total fixed maturity securities-available-for-sale, Unrealized Gains	6.5	6.6
Total fixed maturity securities-available-for-sale, Unrealized Losses	0	0
Total fixed maturity securities-available-for-sale	64.9	65.5
Foreign Government Debt [Member] \| Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale	64.9	65.5
Corporate Bond Securities [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost	6,943.8	6,282.1
Total fixed maturity securities-available-for-sale, Unrealized Gains	367.9	339.6
Total fixed maturity securities-available-for-sale, Unrealized Losses	(39.1)	(76.0)
Total fixed maturity securities-available-for-sale	7,272.6	6,545.7
Corporate Bond Securities [Member] \| Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale	7,272.6	6,545.7
S And P Five Hundred Index Options [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale, Amortized Cost		15.8
Total fixed maturity securities-available-for-sale, Unrealized Gains		0
Total fixed maturity securities-available-for-sale, Unrealized Losses		0
Total fixed maturity securities-available-for-sale		15.8
S And P Five Hundred Index Options [Member] \| Estimate Of Fair Value Fair Value Disclosure [Member]
Schedule of Investments [Line Items]
Total fixed maturity securities-available-for-sale		$ 15.8

Amount of accumulated unrealized gain before deducting unrealized loss on investments in available-for-sale securities impacting investments.

No definition available.

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Amount of accumulated unrealized loss before deducting unrealized gain on investments in available-for-sale securities impacting investments.

+ References

No definition available.

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This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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

-Publisher FASB

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

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