Consolidated Investment Entities (Details 3) (Consolidated Investment Entities, USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Summary of the significant unobservable inputs
Debt	$ 4,595,000,000	$ 4,450,000,000
Other assets
Summary of the significant unobservable inputs
Other assets	1,176,000,000	1,214,000,000
Other assets | Maximum | Discounted cash flow/market comparables
Summary of the significant unobservable inputs
Equivalent yield (as a percent)	14.00%	12.90%
Expected rental value (per square foot)	289	309
Other assets | Minimum | Discounted cash flow/market comparables
Summary of the significant unobservable inputs
Equivalent yield (as a percent)	4.90%	4.10%
Expected rental value (per square foot)	4	4
Other assets | Weighted Average | Discounted cash flow/market comparables
Summary of the significant unobservable inputs
Equivalent yield (as a percent)	7.30%	7.20%
Expected rental value (per square foot)	$ 30	$ 32
Debt | Maximum | Discounted cash flow valuation technique
Summary of the significant unobservable inputs
Annual default rate (as a percent)	4.50%	4.50%
Discount rate (as a percent)	32.00%	30.00%
Constant prepayment rate (as a percent)	10.00%	10.00%
Loss recovery (as a percent)	63.60%	63.60%
Debt | Minimum | Discounted cash flow valuation technique
Summary of the significant unobservable inputs
Annual default rate (as a percent)	2.50%	2.50%
Discount rate (as a percent)	1.50%	1.60%
Constant prepayment rate (as a percent)	5.00%	5.00%
Loss recovery (as a percent)	36.40%	36.40%
Debt | Weighted Average | Discounted cash flow valuation technique
Summary of the significant unobservable inputs
Annual default rate (as a percent)	2.50%	2.50%
Discount rate (as a percent)	2.70%	2.90%
Constant prepayment rate (as a percent)	9.70%	9.60%
Loss recovery (as a percent)	62.10%	62.00%