Fair Value (Estimated Fair Value And The Carrying Value Of Each Financial Instrument) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014 NumberOfDerivativeContracts	Dec. 31, 2013
Total fixed maturity securities-available-for-sale	$ 7,773.7	$ 7,120.5
Commercial mortgage loans, net	5,321.1	5,405.1
Separate account assets	7,179.8us-gaap_SeparateAccountAssets	6,393.2us-gaap_SeparateAccountAssets
Other policyholder funds	6,537.8us-gaap_OtherPolicyholderFunds	6,051.6us-gaap_OtherPolicyholderFunds
Short-term debt	1.1us-gaap_DebtCurrent	1.5us-gaap_DebtCurrent
Long-term debt	503.9	551.9
Level 3 [Member]
Separate account assets	7,179.8
Corporate Bond Securities [Member]
Total fixed maturity securities-available-for-sale	7,272.6	6,545.7
U S Government Agencies Debt Securities [Member]
Total fixed maturity securities-available-for-sale	300.1	353.2
U S States And Political Subdivisions [Member]
Total fixed maturity securities-available-for-sale	136.1	140.3
Foreign Government Debt [Member]
Total fixed maturity securities-available-for-sale	64.9	65.5
S And P Five Hundred Index Options [Member]
Total fixed maturity securities-available-for-sale		15.8
S And P Five Hundred Index Options Purchased Per Month	2
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	7,773.7	7,120.5
Commercial mortgage loans, net	5,321.1	5,405.1
Interest Rate Swaps	4.7
Policy loans	2.2	2.5
Separate account assets		6,393.2
Index-based interest guarantees		67.6
Short-term debt	1.1	1.5
Long-term debt	503.9	551.9
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Corporate Bond Securities [Member]
Total fixed maturity securities-available-for-sale	7,272.6	6,545.7
Index-based interest guarantees	77.0
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| U S Government Agencies Debt Securities [Member]
Total fixed maturity securities-available-for-sale	300.1	353.2
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| U S States And Political Subdivisions [Member]
Total fixed maturity securities-available-for-sale	136.1	140.3
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Foreign Government Debt [Member]
Total fixed maturity securities-available-for-sale	64.9	65.5
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| S And P Five Hundred Index Options [Member]
Total fixed maturity securities-available-for-sale		15.8
Index-based interest guarantees	13.6
Carrying (Reported) Amount, Fair Value Disclosure [Member] \| Investment Type Contracts [Member]
Other policyholder funds	5,961.1	5,469.8
Estimate Of Fair Value Fair Value Disclosure [Member]
Total fixed maturity securities-available-for-sale	7,773.7	7,120.5
Commercial mortgage loans, net	6,021.5	5,769.6
Interest Rate Swaps	4.7
Policy loans	2.2	2.5
Separate account assets	7,179.8	6,393.2
Index-based interest guarantees		67.6
Short-term debt	1.5	1.9
Long-term debt	538.4	553.6
Estimate Of Fair Value Fair Value Disclosure [Member] \| Level 1 [Member]
Separate account assets	7,066.4	6,249.2
Estimate Of Fair Value Fair Value Disclosure [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale	7,684.7	6,988.7
Interest Rate Swaps	4.7
Separate account assets	113.4	144.0
Short-term debt	1.5	1.9
Long-term debt	538.4	553.6
Estimate Of Fair Value Fair Value Disclosure [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale	89.0	131.8
Commercial mortgage loans, net	6,021.5	5,769.6
Policy loans	2.2	2.5
Index-based interest guarantees		67.6
Estimate Of Fair Value Fair Value Disclosure [Member] \| Corporate Bond Securities [Member]
Total fixed maturity securities-available-for-sale	7,272.6	6,545.7
Index-based interest guarantees	77.0
Estimate Of Fair Value Fair Value Disclosure [Member] \| Corporate Bond Securities [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale	7,183.6	6,429.7
Estimate Of Fair Value Fair Value Disclosure [Member] \| Corporate Bond Securities [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale		116.0
Index-based interest guarantees	77.0
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S Government Agencies Debt Securities [Member]
Total fixed maturity securities-available-for-sale	300.1	353.2
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S Government Agencies Debt Securities [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale	300.1	353.2
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S Government Agencies Debt Securities [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale		0
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S States And Political Subdivisions [Member]
Total fixed maturity securities-available-for-sale	136.1	140.3
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S States And Political Subdivisions [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale	136.1	140.3
Estimate Of Fair Value Fair Value Disclosure [Member] \| U S States And Political Subdivisions [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale		0
Estimate Of Fair Value Fair Value Disclosure [Member] \| Foreign Government Debt [Member]
Total fixed maturity securities-available-for-sale	64.9	65.5
Estimate Of Fair Value Fair Value Disclosure [Member] \| Foreign Government Debt [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale	64.9	65.5
Estimate Of Fair Value Fair Value Disclosure [Member] \| Foreign Government Debt [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale		0
Estimate Of Fair Value Fair Value Disclosure [Member] \| S And P Five Hundred Index Options [Member]
Total fixed maturity securities-available-for-sale		15.8
Index-based interest guarantees	13.6
Estimate Of Fair Value Fair Value Disclosure [Member] \| S And P Five Hundred Index Options [Member] \| Level 2 [Member]
Total fixed maturity securities-available-for-sale		0
Estimate Of Fair Value Fair Value Disclosure [Member] \| S And P Five Hundred Index Options [Member] \| Level 3 [Member]
Total fixed maturity securities-available-for-sale		15.8
Index-based interest guarantees	13.6
Estimate Of Fair Value Fair Value Disclosure [Member] \| Investment Type Contracts [Member]
Other policyholder funds	6,232.5	5,632.7
Estimate Of Fair Value Fair Value Disclosure [Member] \| Investment Type Contracts [Member] \| Level 3 [Member]
Other policyholder funds	$ 6,232.5	$ 5,632.7

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Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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The amount of the liability as of the balance sheet date pertaining to the guarantee given by the insurance entity to contract holders of a specified rate of return (a guaranteed yield) on their investments for a specified period.

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Amount before allowance of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums over and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Liability as of the balance sheet date to the policyholders for funds held that are returnable under the terms of insurance contracts that were not separately reported.

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