Fair Value Measurement - Nonrecurring Basis (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended									0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 2 [Member]	Jun. 30, 2013 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member]	Dec. 31, 2012 Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member]	Jun. 30, 2013 Residential Mortgage [Member] Fair Value, Measurements, Nonrecurring [Member] Level 3 [Member]	Jun. 30, 2013 Minimum Broker Price Opinion Valuation Technique [Member] Residential Mortgage [Member]	Jun. 30, 2013 Maximum Broker Price Opinion Valuation Technique [Member] Residential Mortgage [Member]	Jun. 30, 2013 Weighted Average [Member] Broker Price Opinion Valuation Technique [Member] Residential Mortgage [Member]
Assets and liabilities measured at fair value on a nonrecurring basis
Total assets at fair value on a nonrecurring basis					$ 1,600	$ 5,100	$ 95	$ 667	$ 1,500	$ 4,400	$ 1,200
Fair Value Inputs, Liquidation Value Discount												18.00%	59.00%	29.00%
Fair Value, Option, Changes in Fair Value, Gain (Loss)	$ (293)	$ (514)	$ (521)	$ (881)