Derivatives - Derivative Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ (337)	$ (1,217)	$ (4,600)	$ (4,912)
Accrual of periodic settlements
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(540)	(47)	(1,045)	(143)
Accrual of periodic settlements | Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	917	39	1,746	(32)
Accrual of periodic settlements | Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(1,521)	(126)	(2,959)	(220)
Accrual of periodic settlements | Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	64	40	168	109
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Interest Rate Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	1,048	(1,809)	(2,815)	(4,565)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(1,755)	2,060	13,862	7,580
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	2,796	(3,866)	(16,677)	(12,152)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Basis (floating to floating)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	7	(3)	0	7
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Option-based
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(543)	947	2,974	1,408
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Call swaptions | Purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(533)	1,398	3,733	2,981
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Call swaptions | Written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	52	(109)	(340)	(343)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Put swaptions | Purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	43	(355)	(579)	(1,406)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Put swaptions | Written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(15)	19	112	83
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Options on futures
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(13)	0	(19)	0
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Other option-based derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(77)	(6)	67	93
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Other Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(302)	(308)	(3,714)	(1,612)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Futures
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(33)	(262)	(2,481)	(1,283)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Commitments
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(335)	(54)	(1,457)	(366)
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Credit derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	48	0	169	1
Not Designated as Hedging Instrument, Economic Hedge | Derivative gains (losses) excluding accrual of periodic settlements | Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ 18	$ 8	$ 55	$ 36