Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									$ (5,764)	$ 3,280	$ (3,626)
Accrual of periodic settlements	5,142	5,184	4,904	4,738	4,851	5,582	5,667	6,304	19,968	22,404	21,501
Risk management derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									(4,624)	2,779	(1,938)
Risk management derivatives [Member] | Pay-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									(7,703)	14,393	(2,254)
Accrual of periodic settlements									(3,712)	(4,463)	(4,427)
Risk management derivatives [Member] | Receive-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									4,229	(10,721)	1,102
Accrual of periodic settlements									2,600	3,632	2,950
Risk management derivatives [Member] | Basis Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									85	(115)	78
Risk management derivatives [Member] | Foreign Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									27	(101)	59
Risk management derivatives [Member] | Pay-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									(4)	(238)	132
Risk management derivatives [Member] | Receive-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									(197)	307	410
Risk management derivatives [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									1	21	(35)
Accrual of periodic settlements									50	64	47
Mortgage commitment derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value (losses) gains, net									$ (1,140)	$ 501	$ (1,688)