Fair Value Measurement Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details 6a) (USD $)	12 Months Ended										0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Residential Mortgage [Member] Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Broker Price Opinion Valuation Technique [Member] Minimum [Member] Residential Mortgage [Member]	Dec. 31, 2012 Broker Price Opinion Valuation Technique [Member] Maximum [Member] Residential Mortgage [Member]	Dec. 31, 2012 Broker Price Opinion Valuation Technique [Member] Weighted Average [Member] Residential Mortgage [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure, Nonrecurring				$ 5,100,000,000	$ 5,300,000,000	$ 667,000,000	$ 369,000,000	$ 4,400,000,000	$ 4,900,000,000	$ 4,000,000,000
Fair Value Inputs, Liquidation Value Discount											22.00%	66.00%	29.00%
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ (1,600,000,000)	$ 2,200,000,000	$ (3,600,000,000)