Variable Interest Entities (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Sponsored Investment Funds
Total assets of unconsolidated money market mutual fund variable interest entities	$ 1,200,000,000	$ 1,400,000,000
Other investments: Other limited partnership and fund interests
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	190,700,000	188,200,000
Maximum exposure to loss	190,700,000	188,200,000
Available-for-sale \| Corporate debt securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	466,400,000	456,700,000
Maximum exposure to loss	357,300,000	353,300,000
Available-for-sale \| Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	2,823,500,000	2,822,900,000
Maximum exposure to loss	2,688,800,000	2,702,900,000
Available-for-sale \| Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	3,911,300,000	3,975,500,000
Maximum exposure to loss	3,822,000,000	3,896,900,000
Available-for-sale \| Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	532,900,000	504,100,000
Maximum exposure to loss	549,900,000	521,200,000
Available-for-sale \| Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	4,648,200,000	4,616,400,000
Maximum exposure to loss	4,598,200,000	4,583,400,000
Trading \| Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	32,100,000	34,400,000
Maximum exposure to loss	32,100,000	34,400,000
Trading \| Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	1,800,000	1,500,000
Maximum exposure to loss	1,800,000	1,500,000
Trading \| Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	39,800,000	39,400,000
Maximum exposure to loss	39,800,000	39,400,000
Trading \| Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value		200,000
Maximum exposure to loss		$ 200,000

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Total assets held by money market mutual funds that are deemed to be variable interest entities but are not consolidated by the entity, as it is not the primary beneficiary.

+ References

No definition available.

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5747-111685

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- Definition

Carrying amount of the assets in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), where the reporting entity is not the VIE's primary beneficiary.

+ References

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