Loans and ACL - Collectively Evaluated for Impairment (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Recorded Investment	$ 144,491	$ 142,044
Related ALLL	1,350	1,319
Commercial | Commercial and industrial
Recorded Investment	60,141	58,804
Related ALLL	502	494
Commercial | CRE
Recorded Investment	21,512	21,173
Related ALLL	181	154
Commercial | Lease financing
Recorded Investment	1,915	1,910
Related ALLL	10	9
Retail | Residential mortgage
Recorded Investment	29,116	27,914
Related ALLL	154	143
Retail | Direct
Recorded Investment	11,590	11,815
Related ALLL	91	98
Retail | Indirect
Recorded Investment	16,837	16,935
Related ALLL	300	296
Revolving credit
Recorded Investment	2,847	2,842
Related ALLL	94	97
PCI
Recorded Investment	533	651
Related ALLL	$ 18	$ 28