Loans and Allowance for Credit Losses, Significant Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	$ 675	$ 405	$ 1,007	$ 661
Sales	(688)	(382)	(1,288)	(842)
Transfers to MLHFS/LHFS	(1,941)	(172)	(1,944)	(2,145)
Total Commercial [Member]
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	670	398	999	654
Sales	(535)	(294)	(956)	(754)
Transfers to MLHFS/LHFS	(89)	(100)	(92)	(520)
Total Consumer [Member]
Loans and Allowance for Credit Losses, Significant Activity [Abstract]
Purchases	5	7	8	7
Sales	(153)	(88)	(332)	(88)
Transfers to MLHFS/LHFS	$ (1,852)	$ (72)	$ (1,852)	$ (1,625)