Fair Value Measurements (Details 7) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Assets (liabilities)
Mortgage loans	$ 11,899.5	$ 11,811.6
Policy loans	826.0us-gaap_LoansInsurancePolicy	829.2us-gaap_LoansInsurancePolicy
Short-term debt	(27.2)us-gaap_ShortTermBorrowings	(28.0)us-gaap_ShortTermBorrowings
Long-term debt	(2,514.6)us-gaap_LongTermDebt	(2,531.2)us-gaap_LongTermDebt
Fair value hierarchy Level 1
Assets (liabilities)
Cash and cash equivalents not required to be reported at fair value	707.9	822.2
Bank deposits	(1,339.4)	(1,343.8)
Cash collateral payable	(231.9)	(148.3)
Fair value hierarchy Level 2
Assets (liabilities)
Other investments	178.2	183.7
Investment-type insurance contracts	(5,062.8)	(5,455.4)
Short-term debt	(27.2)	(28.0)
Long-term debt	(2,753.1)	(2,703.8)
Bank deposits	(631.3)	(641.7)
Fair value hierarchy Level 3
Assets (liabilities)
Mortgage loans	12,494.4	12,350.2
Policy loans	1,067.2	1,083.2
Other investments	80.0	27.9
Investment-type insurance contracts	(22,672.5)	(22,867.3)
Long-term debt	(65.6)	(82.3)
Separate account liabilities	(130,253.7)	(127,131.0)
Carrying amount
Assets (liabilities)
Mortgage loans	11,899.5	11,811.6
Policy loans	826.0	829.2
Other investments	253.5	211.2
Cash and cash equivalents not required to be reported at fair value	707.9	822.2
Investment-type insurance contracts	(27,605.6)	(28,256.3)
Short-term debt	(27.2)	(28.0)
Long-term debt	(2,514.6)	(2,531.2)
Separate account liabilities	(131,598.5)	(128,480.5)
Bank deposits	(1,966.2)	(1,979.7)
Cash collateral payable	(231.9)	(148.3)
Assets (liabilities) measured at fair value
Assets (liabilities)
Mortgage loans	12,494.4	12,350.2
Policy loans	1,067.2	1,083.2
Other investments	258.2	211.6
Cash and cash equivalents not required to be reported at fair value	707.9	822.2
Investment-type insurance contracts	(27,735.3)	(28,322.7)
Short-term debt	(27.2)	(28.0)
Long-term debt	(2,818.7)	(2,786.1)
Separate account liabilities	(130,253.7)	(127,131.0)
Bank deposits	(1,970.7)	(1,985.5)
Cash collateral payable	$ (231.9)	$ (148.3)

Includes currency on hand and other cash equivalents not required to be reported at fair value.

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This item represents the obligation to return cash received as collateral from counterparties.

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This item represents investment-type insurance contracts such as guaranteed investment contracts and funding arrangements that do not have significant insurance risk. This item excludes any embedded derivatives within investment-type insurance host contracts that are required to be reported at fair value.

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This item represents invested assets not specifically identified in the statement of financial position, excluding derivative assets. This includes invested assets such as seed money and commercial mortgage loans of consolidated variable interest entities reported at fair value.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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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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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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