Loans and Related Allowance for Credit Losses, Allowance by Credit Impairment Methodology (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans		$ 12,022	$ 10,456	$ 10,821
Loans	[1]	1,009,843	962,265
Total Commercial [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans		5,279	6,245	6,428
Loans		567,735	515,719
Total Consumer [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans		6,743	4,211	$ 4,393
Loans		$ 442,108	446,546
Non-PCI [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for credit losses, collectively evaluated			9,142
Allowance for credit losses, individually evaluated			1,314
Recorded investment in loans, collectively evaluated			948,667
Recorded investment in loans, individually evaluated			13,030
Non-PCI [Member] | Total Commercial [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for credit losses, collectively evaluated			5,778
Allowance for credit losses, individually evaluated			467
Recorded investment in loans, collectively evaluated			512,586
Recorded investment in loans, individually evaluated			3,133
Non-PCI [Member] | Total Consumer [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Allowance for credit losses, collectively evaluated			3,364
Allowance for credit losses, individually evaluated			847
Recorded investment in loans, collectively evaluated			436,081
Recorded investment in loans, individually evaluated			9,897
Loans			445,978
PCI [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans			0
Loans			568
PCI [Member] | Total Commercial [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans			0
Loans			0
PCI [Member] | Total Consumer [Member]
Loans and Allowance for Credit Losses, by Credit Impairment Method [Abstract]
Total allowance for credit losses for loans			0
Loans			$ 568

[1] (2) Parenthetical amounts represent assets and liabilities that we are required to carry at fair value or have elected the fair value option.