Derivative Instruments FV Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (1,324)		$ (4,255)		$ (3,733)		$ (5,793)
Risk Management Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(508)		(4,067)		(2,150)		(5,567)
Risk Management Derivatives [Member] | Pay-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(2,272)		(11,334)		(6,955)		(16,206)
Risk Management Derivatives [Member] | Receive-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	1,511		4,577		4,185		7,105
Risk Management Derivatives [Member] | Basis Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	42		75		98		104
Risk Management Derivatives [Member] | Foreign Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	61		31		70		114
Risk Management Derivatives [Member] | Pay-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	51		533		108		805
Risk Management Derivatives [Member] | Receive-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	123		2,091		374		2,591
Risk Management Derivatives [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(24)	[1]	(40)	[1]	(30)	[1]	(80)	[1]
Mortgage Commitment Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (816)		$ (188)		$ (1,583)		$ (226)

[1] Includes interest rate caps, futures, swap credit enhancements and mortgage insurance contracts.