Variable Interest Entities (Details 2) (USD $)	Mar. 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 interests
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	137,400,000	123,500,000
Maximum exposure to loss	137,400,000	123,500,000
Available-for-sale | Corporate debt securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	542,800,000	523,400,000
Maximum exposure to loss	451,100,000	448,200,000
Available-for-sale | Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	2,900,900,000	2,845,200,000
Maximum exposure to loss	2,834,400,000	2,799,100,000
Available-for-sale | Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	4,087,100,000	4,026,400,000
Maximum exposure to loss	4,064,000,000	4,078,000,000
Available-for-sale | Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	380,900,000	363,400,000
Maximum exposure to loss	407,100,000	391,900,000
Available-for-sale | Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	4,277,200,000	4,167,800,000
Maximum exposure to loss	4,252,100,000	4,157,500,000
Trading | Residential mortgage-backed pass-through securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	42,500,000	47,500,000
Maximum exposure to loss	42,500,000	47,500,000
Trading | Commercial mortgage-backed securities
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	1,600,000	1,800,000
Maximum exposure to loss	1,600,000	1,800,000
Trading | Collateralized debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	64,200,000	59,600,000
Maximum exposure to loss	64,200,000	59,600,000
Trading | Other debt obligations
Unconsolidated Variable Interest Entity disclosures
Asset carrying value	1,000,000	1,200,000
Maximum exposure to loss	$ 1,000,000	$ 1,200,000