Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	$ (569)	$ (853)	$ (1,934)	$ (1,548)
Net contractual interest expense on interest-rate swaps	5,777	5,227	11,124	10,023
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(94)	(2,164)	(4,123)	(3,499)
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	191	1,884	3,534	3,165
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	17	27	73	51
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	4	(17)	(34)	2
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(13)	(143)	(161)	(320)
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	25	93	657	100
Future [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(4)	195	(75)	254
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	62	(367)	(299)	(755)
Net contractual interest expense on interest-rate swaps	(64)	(242)	(170)	(508)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(662)	(469)	(1,655)	(769)
Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	$ 31	$ (17)	$ 20	$ (24)