Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (2,765)	$ (480)	$ (2,037)	$ (3,011)
Accrual of periodic settlements	5,588	5,184	16,332	14,826
Risk Management Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(2,404)	(407)	(1,610)	(2,283)
Risk Management Derivatives [Member] | Pay-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(4,402)	712	(3,120)	(3,755)
Accrual of periodic settlements	(895)	(939)	(2,730)	(2,755)
Risk Management Derivatives [Member] | Receive-fixed Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	2,295	(822)	2,236	2,282
Accrual of periodic settlements	620	613	2,007	1,946
Risk Management Derivatives [Member] | Basis Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	37	6	25	49
Risk Management Derivatives [Member] | Foreign Currency Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(20)	(17)	(33)	21
Risk Management Derivatives [Member] | Pay-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	32	(53)	137	(90)
Risk Management Derivatives [Member] | Receive-fixed Swaption [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(102)	82	(181)	(19)
Risk Management Derivatives [Member] | Other [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	22	(1)	20	(1)
Accrual of periodic settlements	9	12	29	39
Mortgage commitment derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (361)	$ (73)	$ (427)	$ (728)