Consolidated Investment Entities - Fair Value Measurements for Level 3 Assets and Liabilities (Details) (Consolidated investment entities, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Assets measured on recurring basis \| Level 3
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	$ 2,931.2	$ 2,860.3
Gains (Losses) Included in the Condensed Consolidated Statement of Operations	211.0	282.2
Purchases	848.0	389.8
Sales	(771.6)	(601.1)
Transfers in to Level 3	25.5	0
Transfers out of Level 3	(484.5)	0
Assets, Fair Value, ending balance	2,759.6	2,931.2
Liabilities, Fair Value, beginning balance	(3,829.4)	(2,057.1)
Gains (Losses) Included in the Condensed Consolidated Statement of Operations	(6.3)	(173.1)
Purchases	(1,594.1)	(1,603.6)
Sales	268.2	4.4
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Liabilities, Fair Value, ending balance	(5,161.6)	(3,829.4)
VOEs \| Limited partnerships \| Assets measured on recurring basis \| Level 3
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	2,931.2	2,860.3
Gains (Losses) Included in the Condensed Consolidated Statement of Operations	211.0	282.2
Purchases	848.0	389.8
Sales	(771.6)	(601.1)
Transfers in to Level 3	0	0
Transfers out of Level 3	(484.5)	0
Assets, Fair Value, ending balance	2,734.1	2,931.2
VIEs \| Loans Receivable \| Assets measured on recurring basis \| Level 3
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	0	0
Gains (Losses) Included in the Condensed Consolidated Statement of Operations	0	0
Purchases	0	0
Sales	0	0
Transfers in to Level 3	25.5	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	25.5	0
VIEs \| Collateralized Debt Obligations \| Assets measured on recurring basis \| Level 3
Fixed Maturities and Equity Securities Rollforward:
Liabilities, Fair Value, beginning balance	(3,829.4)	(2,057.1)
Gains (Losses) Included in the Condensed Consolidated Statement of Operations	(6.3)	(173.1)
Purchases	(1,594.1)	(1,603.6)
Sales	268.2	4.4
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Liabilities, Fair Value, ending balance	(5,161.6)	(3,829.4)
Collateralized Debt Obligations \| VIEs
Fixed Maturities and Equity Securities Rollforward:
Liabilities, Fair Value, ending balance	(5,161.6)	(3,829.4)
Loans Receivable \| VIEs
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, ending balance	$ 25.5

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Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy.

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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