Loans and ACL - Collectively Evaluated for Impairment (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Recorded Investment	$ 145,007	$ 142,044
Related ALLL	1,366	1,319
Commercial | Commercial and industrial
Recorded Investment	59,380	58,804
Related ALLL	513	494
Commercial | CRE
Recorded Investment	21,383	21,173
Related ALLL	182	154
Commercial | Lease financing
Recorded Investment	2,022	1,910
Related ALLL	10	9
Retail | Residential mortgage
Recorded Investment	29,980	27,914
Related ALLL	160	143
Retail | Direct
Recorded Investment	11,549	11,815
Related ALLL	92	98
Retail | Indirect
Recorded Investment	17,154	16,935
Related ALLL	298	296
Revolving credit
Recorded Investment	3,042	2,842
Related ALLL	101	97
PCI
Recorded Investment	497	651
Related ALLL	$ 10	$ 28