Derivative Instruments Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	$ (1,365)	$ (695)
Net accrual of periodic settlements	5,347	4,796
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(4,029)	(1,335)
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	3,343	1,281
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	56	24
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(38)	19
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(148)	(177)
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	632	7
Future [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(71)	59
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(361)	(388)
Net accrual of periodic settlements	(106)	(266)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	(993)	(300)
Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Fair Value Gain (Loss) on Derivative, Net	$ (11)	$ (7)