Consolidated Investment Products (Level 3 Valuation Techniques) (Details) In Millions, unless otherwise specified													3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended						9 Months Ended
	Sep. 30, 2013 USD ($)	Dec. 31, 2012 USD ($)	Sep. 30, 2013 Significant Unobservable Inputs [Member] USD ($)	Dec. 31, 2012 Significant Unobservable Inputs [Member] USD ($)	Sep. 30, 2013 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] USD ($)	Dec. 31, 2012 Asset-backed Securities [Member] Significant Unobservable Inputs [Member] USD ($)	Sep. 30, 2013 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Minimum [Member]	Dec. 31, 2012 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Minimum [Member]	Sep. 30, 2013 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Maximum [Member]	Dec. 31, 2012 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Maximum [Member]	Sep. 30, 2013 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Weighted Average [Member]	Dec. 31, 2012 Market Comparable [Member] Private Equity Fund, Equity Securities [Member] Significant Unobservable Inputs [Member] Weighted Average [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Minimum [Member] EURIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Minimum [Member] EURIBOR [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Minimum [Member] LIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Minimum [Member] LIBOR [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Maximum [Member] EURIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Maximum [Member] EURIBOR [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Maximum [Member] LIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Maximum [Member] LIBOR [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Weighted Average [Member] EURIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Weighted Average [Member] EURIBOR [Member]	Sep. 30, 2013 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Weighted Average [Member] LIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] CLO Notes [Member] Significant Unobservable Inputs [Member] Weighted Average [Member] LIBOR [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Real Estate Investment [Member] Significant Unobservable Inputs [Member] Minimum [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Real Estate Investment [Member] Significant Unobservable Inputs [Member] Maximum [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Real Estate Investment [Member] Significant Unobservable Inputs [Member] Weighted Average [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Real Estate Investment [Member] Significant Unobservable Inputs [Member] Minimum Weighted Average [Member]	Dec. 31, 2012 Discounted Cash Flow [Member] Real Estate Investment [Member] Significant Unobservable Inputs [Member] Maximum Weighted Average [Member]	Sep. 30, 2013 2012 and Thereafter [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Private equity fund assets			$ 58.6	$ 94.1
Real estate investments				5.3
Total liabilities	$ (9,644.1)	$ (8,443.4)			$ (4,003.1)	$ (3,899.4)
Revenue Multiple							100.00%	100.00%	500.00%	400.00%	300.00%	190.00%
Discount Rate							24.00%	15.00%	50.00%	50.00%	28.20%	27.50%													6.75%	7.00%	6.86%
In-Place Rent Rates (in JPY per sqft)																									218	397		231	384
Market Rent Rates (in JPY per sqft)																									333	417		348	379
Revenue Growth Rate																											2.18%
Exit Capitalization Rate																									7.00%	7.25%	7.11%
Stabilized Occupancy Rate																											95.00%
Expense Growth Rate																											1.00%
Probability of Default													4.70%	3.00%	1.00%	1.00%	5.00%	5.00%	3.00%	3.00%										1.40%
Assumed Default Rate, less than one year																					4.70%	3.30%	1.60%	1.10%
Assumed Default Rate, more than one year																					5.00%	5.00%	3.00%	3.00%
Spread over variable rate													1.50%	3.25%	1.28%	1.30%	10.80%	19.20%	8.82%	16.32%	2.94%	5.63%	2.02%	3.23%