Loans and ACL - Collectively Evaluated for Impairment (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Recorded Investment	$ 141,320	$ 142,044
Related ALLL	1,322	1,319
Commercial | Commercial and industrial
Recorded Investment	58,793	58,804
Related ALLL	497	494
Commercial | CRE
Recorded Investment	21,391	21,173
Related ALLL	164	154
Commercial | Lease financing
Recorded Investment	1,873	1,910
Related ALLL	9	9
Retail | Residential mortgage
Recorded Investment	27,953	27,914
Related ALLL	149	143
Retail | Direct
Recorded Investment	11,601	11,815
Related ALLL	92	98
Retail | Indirect
Recorded Investment	16,383	16,935
Related ALLL	293	296
Revolving credit
Recorded Investment	2,737	2,842
Related ALLL	93	97
PCI
Recorded Investment	589	651
Related ALLL	$ 25	$ 28