Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Net accrual of periodic settlements	$ 5,286	$ 5,677	$ 10,055	$ 10,744
Derivative fair value gains (losses), net	(1,557)	2,481	(4,290)	728
Risk Management Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(1,190)	2,308	(3,561)	794
Risk Management Derivatives [Member] | Pay-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(2,257)	4,351	(7,430)	1,282
Risk Management Derivatives [Member] | Receive-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	1,371	(1,906)	4,358	(59)
Risk Management Derivatives [Member] | Basis Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	14	(44)	49	(12)
Risk Management Derivatives [Member] | Foreign Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(34)	16	(31)	(13)
Risk Management Derivatives [Member] | Pay-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	4	14	29	105
Risk Management Derivatives [Member] | Receive-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(19)	80	(136)	(79)
Risk Management Derivatives [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	22	(4)	160	(2)
Risk Management Derivatives [Member] | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net accrual of periodic settlements	(291)	(199)	(560)	(428)
Mortgage commitment derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (367)	$ 173	$ (729)	$ (66)