Consolidated Investment Products (Level 3 Valuation Techniques) (Details) In Millions, unless otherwise specified	Jun. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Jun. 30, 2012 Significant Unobservable Inputs [Member] USD ($)		Dec. 31, 2011 Significant Unobservable Inputs [Member] USD ($)	Jun. 30, 2012 Significant Unobservable Inputs [Member] Minimum [Member] EURIBOR [Member]	Jun. 30, 2012 Significant Unobservable Inputs [Member] Minimum [Member] LIBOR [Member]	Jun. 30, 2012 Significant Unobservable Inputs [Member] Maximum [Member] EURIBOR [Member]	Jun. 30, 2012 Significant Unobservable Inputs [Member] Maximum [Member] LIBOR [Member]	Jun. 30, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] USD ($)	Dec. 31, 2011 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] USD ($)	Jun. 30, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] Minimum [Member] EURIBOR [Member]		Jun. 30, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] Minimum [Member] LIBOR [Member]		Jun. 30, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] Maximum [Member] EURIBOR [Member]		Jun. 30, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] Maximum [Member] LIBOR [Member]		Jun. 30, 2012 Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Minimum [Member] Market Comparable [Member]	Jun. 30, 2012 Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Maximum [Member] Market Comparable [Member]	Jun. 30, 2012 Real Estate Investment [Member] Significant Unobservable Inputs [Member] Cash Flow Hedging [Member]	Jun. 30, 2012 Real Estate Investment [Member] Significant Unobservable Inputs [Member] Minimum [Member] Market Comparable [Member]	Jun. 30, 2012 Real Estate Investment [Member] Significant Unobservable Inputs [Member] Minimum [Member] Cash Flow Hedging [Member]	Jun. 30, 2012 Real Estate Investment [Member] Significant Unobservable Inputs [Member] Maximum [Member] Market Comparable [Member]	Jun. 30, 2012 Real Estate Investment [Member] Significant Unobservable Inputs [Member] Maximum [Member] Cash Flow Hedging [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private equity fund assets			$ 125.8	[1]	$ 126.7
Real estate investments			152.6	[1]	232.9
Total liabilities	$ (9,494.1)	$ (10,209.4)								$ (5,069.7)	$ (5,512.9)
EBITDA Multiple																				3000.00%	4000.00%
Revenue Multiple																				500.00%	1500.00%
Discount Rate																				20.00%	50.00%			5.75%		8.00%
In-Place & Market Rent Rates (in JPY per sqft)																							250	250	700	700
Revenue Growth Rate																								0.00%		2.00%
Exit Capitalization Rate																							6.00%	6.00%	8.25%	8.25%
Stabilized Occupancy Rate																								92.00%		96.00%
Expense Growth Rate																						1.00%
Probability of Default						1.00%	1.00%	5.00%	4.00%			1.00%		1.00%		5.00%		4.00%
Spread over variable rate						21.50%	13.50%	28.50%	18.00%			3.00%	[2]	2.00%	[2]	28.50%	[2]	18.00%	[2]

[1] Certain equity securities held by consolidated private equity funds are valued using third-party pricing information and/or recent private market transactions. Quantitative unobservable inputs for such valuations were not developed or adjusted by the company. Debt securities held by consolidated private equity funds of $11.9 million are excluded from the table above as they are valued using a cost valuation technique. Investments in other private equity funds of $564.3 million are also excluded from the table above as they are valued using the NAV practical expedient.

[2] Lower spreads relate to the more senior tranches in the CLO note structure; higher spreads relate to the less senior tranches.