Quantitative Information about Level 3 Fair Value Measurements of Assets (Detail) (USD $) In Millions, unless otherwise specified						6 Months Ended									6 Months Ended				6 Months Ended						6 Months Ended									6 Months Ended
	Jun. 30, 2012 Fair Value, Measurements, Recurring	Dec. 31, 2011 Fair Value, Measurements, Recurring	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3	Dec. 31, 2011 Fair Value, Measurements, Recurring Level 3	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Available-for-sale State And Political Subdivisions Discounted Cash Flow	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Available-for-sale State And Political Subdivisions Discounted Cash Flow Minimum	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Available-for-sale State And Political Subdivisions Discounted Cash Flow Maximum	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Debt Option Pricing Model		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Debt Option Pricing Model Minimum		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Debt Option Pricing Model Maximum		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Distressed Debt Discounted Cash Flow	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Distressed Debt Discounted Cash Flow Minimum	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Distressed Debt Discounted Cash Flow Maximum	Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Foreign Exchange Swaptions Option Pricing Model		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Foreign Exchange Swaptions Option Pricing Model Minimum		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Structured Foreign Exchange Swaptions Option Pricing Model Maximum		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Equity Options Option Pricing Model		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Equity Options Option Pricing Model Minimum		Jun. 30, 2012 Fair Value, Measurements, Recurring Level 3 Trading Assets Equity Options Option Pricing Model Maximum		Jun. 30, 2012 Fair Value, Measurements, Nonrecurring	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring Level 3	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring Level 3	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring Level 3 Loans Discounted Cash Flow	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring Level 3 Loans Discounted Cash Flow Minimum	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring Level 3 Loans Discounted Cash Flow Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value of assets	$ 103,822	$ 99,533	$ 313	$ 365	$ 42			$ 30	[1]					$ 30			$ 34	[1]					$ 39	[1]					$ 307	$ 347	$ 35	$ 43	$ 35
Expected credit loss						8.00%	39.00%
Correlation risk								15.00%	[1]										0.00%	[1]	25.00%	[1]
Volatility										13.00%	[1]	17.00%	[1]						12.00%	[1]	17.00%	[1]			24.00%	[1]	33.00%	[1]
Expected maturity															2 years	10 years
Timing of sale																																		0 months	18 months
Credit spreads															1.00%	8.00%
Cap rate																																		5.50%	8.00%
Cost to complete/sell																																		0.00%	29.00%

[1] The option pricing model uses market inputs such as foreign currency exchange rates, interest rates and volatility to calculate the fair value of the option.