Fair Value (Fair Value Measurements- Recurring Quantitative Information) (Details) (Fair Value, Measurements, Recurring [Member], Level 3 [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ 10,889
Recurring Liabilities - Fair Value	330
Total Recurring Assets Net of Recurring Liabilities - Fair Value	10,559
Black Rock LTIP [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	210
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	6,220
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Third Party Pricing Services Available [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	5,246
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Third Party Pricing Services Unavailable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	974
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Constant Prepayment Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	1.00%
Range (Maximum % or bps amount)	30.00%
Weighted Average (% or bps amount)	5.00%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Constant Default Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	0.00%
Range (Maximum % or bps amount)	24.00%
Weighted Average (% or bps amount)	7.00%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Loss Severity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	10.00%
Range (Maximum % or bps amount)	92.00%
Weighted Average (% or bps amount)	51.00%
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Spread Over The Benchmark Curve [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted Average (% or bps amount)	3.50%
Available-for-sale Securities [Member] | Asset backed [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	714
Available-for-sale Securities [Member] | Asset backed [Member] | Third Party Pricing Services Available [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	686
Available-for-sale Securities [Member] | Asset backed [Member] | Third Party Pricing Services Unavailable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	28
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Constant Prepayment Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	1.00%
Range (Maximum % or bps amount)	15.00%
Weighted Average (% or bps amount)	3.00%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Constant Default Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	1.00%
Range (Maximum % or bps amount)	25.00%
Weighted Average (% or bps amount)	9.00%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Loss Severity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	10.00%
Range (Maximum % or bps amount)	100.00%
Weighted Average (% or bps amount)	72.00%
Available-for-sale Securities [Member] | Asset backed [Member] | Priced By Third Party Vendor Using Discounted Cash Flow Pricing Model [Member] | Spread Over The Benchmark Curve [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted Average (% or bps amount)	5.18%
Available-for-sale Securities [Member] | State and Municipal [Member] | Discounted Cash Flow [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	158
Available-for-sale Securities [Member] | State and Municipal [Member] | Discounted Cash Flow [Member] | Spread Over The Benchmark Curve [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	1.10%
Range (Maximum % or bps amount)	2.75%
Weighted Average (% or bps amount)	1.62%
Available-for-sale Securities [Member] | State and Municipal [Member] | Consensus Pricing [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	183
Available-for-sale Securities [Member] | State and Municipal [Member] | Consensus Pricing [Member] | Credit And Liquidity Discount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	0.00%
Range (Maximum % or bps amount)	30.00%
Weighted Average (% or bps amount)	9.00%
Available-for-sale Securities [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	52
Available-for-sale Securities [Member] | Other Debt Securities [Member] | Consensus Pricing [Member] | Credit And Liquidity Discount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	7.00%
Range (Maximum % or bps amount)	95.00%
Weighted Average (% or bps amount)	86.00%
Derivative [Member] | Residential Mortgage Loans Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	123
Derivative [Member] | Other Contracts Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	77
Derivative [Member] | Interest Rate Contracts [Member] | Residential Mortgage Loans Commitments [Member] | Discounted Cash Flow [Member] | Probability Of Funding [Member] | Financial Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	5.00%
Range (Maximum % or bps amount)	99.00%
Weighted Average (% or bps amount)	65.20%
Derivative [Member] | Interest Rate Contracts [Member] | Residential Mortgage Loans Commitments [Member] | Discounted Cash Flow [Member] | Embedded Servicing Value [Member] | Financial Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	0.40%
Range (Maximum % or bps amount)	1.20%
Weighted Average (% or bps amount)	0.80%
Derivative [Member] | Interest Rate Contracts [Member] | Commercial Mortgage Loans Commitments [Member] | Financial Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	13
Derivative [Member] | Interest Rate Contracts [Member] | Commercial Mortgage Loans Commitments [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	13
Derivative [Member] | Interest Rate Contracts [Member] | Interest Rate Options [Member] | Financial Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	4
Derivative [Member] | Interest Rate Contracts [Member] | Interest Rate Options [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	3
Derivative [Member] | Black Rock LTIP [Member] | Consensus Pricing [Member] | Liquidity Discount [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	22.50%
Range (Maximum % or bps amount)	22.50%
Weighted Average (% or bps amount)	22.50%
Derivative [Member] | Other Contract [Member] | Risk Participations [Member] | Financial Derivative Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	7
Derivative [Member] | Other Contract [Member] | Risk Participations [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Liabilities - Fair Value	6
Derivative [Member] | Other Contract [Member] | Other Contracts Liabilities [Member] | Discounted Cash Flow [Member] | Spread Over The Benchmark Curve [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	0.94%
Range (Maximum % or bps amount)	0.94%
Weighted Average (% or bps amount)	0.94%
Derivative [Member] | Other Contract [Member] | Other Contracts Liabilities [Member] | Discounted Cash Flow [Member] | Credit And Liquidity Discount [Member] | Financial Derivative Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	39.00%
Range (Maximum % or bps amount)	99.00%
Weighted Average (% or bps amount)	48.00%
Trading Securities - Debt [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	32
Trading Securities - Debt [Member] | Consensus Pricing [Member] | Credit And Liquidity Discount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	8.00%
Range (Maximum % or bps amount)	40.00%
Weighted Average (% or bps amount)	16.00%
Residential Mortgage Servicing Rights MSRs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	594
Residential Mortgage Servicing Rights MSRs [Member] | Discounted Cash Flow [Member] | Constant Prepayment Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	3.90%
Range (Maximum % or bps amount)	57.80%
Weighted Average (% or bps amount)	20.80%
Residential Mortgage Servicing Rights MSRs [Member] | Discounted Cash Flow [Member] | Spread Over The Benchmark Curve [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	9.39%
Range (Maximum % or bps amount)	19.37%
Weighted Average (% or bps amount)	11.25%
Assets Held-for-sale [Member] | Commercial Mortgages [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	811
Assets Held-for-sale [Member] | Commercial Mortgages [Member] | Discounted Cash Flow [Member] | Spread Over The Benchmark Curve [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	4.95%
Range (Maximum % or bps amount)	33.20%
Weighted Average (% or bps amount)	9.62%
Equity Investments [Member] | Direct Investments Equity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	1,094
Equity Investments [Member] | Direct Investments Equity [Member] | Multiple Of Adjusted Earnings [Member] | Multiple Of Earnings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum Amount)	4.5
Range (Maximum Amount)	11.0
Weighted Average (Amount)	6.5
Equity Investments [Member] | Indirect Investments Equity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	658
Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	7
Other Assets [Member] | Black Rock Series C Preferred Stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	210
Other Assets [Member] | Black Rock Series C Preferred Stock [Member] | Consensus Pricing [Member] | Liquidity Discount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range (Minimum % or bps amount)	22.50%
Range (Maximum % or bps amount)	22.50%
Weighted Average (% or bps amount)	22.50%
Insignificant Assets, Net of Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Recurring Assets - Fair Value	$ (3)