Fair Value Measurements - Additional Information (Parenthetical) (Detail) (USD $)							3 Months Ended
	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2011 Software and Software Development Costs [Member]	Mar. 31, 2011 Software and Software Development Costs [Member]	Sep. 30, 2012 Trading Derivative Liabilities Fair Value, Measurements, Recurring	Dec. 31, 2011 Trading Derivative Liabilities Fair Value, Measurements, Recurring	Sep. 30, 2012 Derivative Assets [Member]	Sep. 30, 2011 Derivative Assets [Member]	Sep. 30, 2012 Derivative Liabilities	Sep. 30, 2011 Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of the derivative asset									$ 9,100,000,000	$ 8,800,000,000
Fair value of the derivative liability									13,700,000,000	6,800,000,000
Net Derivatives	3,555,000,000	4,006,000,000	4,157,000,000	4,370,000,000	4,090,000,000	3,500,000,000					1,800,000,000	2,800,000,000	1,400,000,000	1,300,000,000
Additional Charge related to Impairment of capitalized software development costs							$ 16,000,000	$ 78,000,000