Variable Interest Entities (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Sponsored Investment Funds
Total assets of unconsolidated money market mutual fund variable interest entities	$ 1,400,000,000	$ 1,400,000,000
Other investments: Other limited partnership and fund interests
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	188,200,000	123,500,000
Maximum exposure to loss	188,200,000	123,500,000
Available-for-sale \| Corporate debt securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	456,700,000	523,400,000
Maximum exposure to loss	353,300,000	448,200,000
Available-for-sale \| Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	2,822,900,000	2,845,200,000
Maximum exposure to loss	2,702,900,000	2,799,100,000
Available-for-sale \| Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	3,975,500,000	4,026,400,000
Maximum exposure to loss	3,896,900,000	4,078,000,000
Available-for-sale \| Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	504,100,000	363,400,000
Maximum exposure to loss	521,200,000	391,900,000
Available-for-sale \| Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	4,616,400,000	4,167,800,000
Maximum exposure to loss	4,583,400,000	4,157,500,000
Trading \| Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	34,400,000	47,500,000
Maximum exposure to loss	34,400,000	47,500,000
Trading \| Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	1,500,000	1,800,000
Maximum exposure to loss	1,500,000	1,800,000
Trading \| Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	39,400,000	59,600,000
Maximum exposure to loss	39,400,000	59,600,000
Trading \| Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	200,000	1,200,000
Maximum exposure to loss	$ 200,000	$ 1,200,000

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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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