Loans and Allowance for Loan Losses - Aging of Balance of Loans Held for Investment By Class (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Aging of loans
Current		$ 89,121	$ 87,798
30 to 89 Days Past Due		538	283
90 Days or More Past Due		127	132
Total past due		665	415
Loans held for investment	[1]	89,786	88,213
Loans 90 days or more past due and still accruing		18	20
Commercial
Aging of loans
Current		49,123	45,610
30 to 89 Days Past Due		204	71
90 Days or More Past Due		51	64
Total past due		255	135
Loans held for investment		49,378	45,745
Loans 90 days or more past due and still accruing		2	3
Commercial | Construction
Aging of loans
Loans held for investment		1,583
Consumer
Aging of loans
Current		39,998	42,188
30 to 89 Days Past Due		334	212
90 Days or More Past Due		76	68
Total past due		410	280
Loans held for investment		40,408	42,468
Loans 90 days or more past due and still accruing		16	17
residential mortgage and home equity [Member] | Consumer Loans
Aging of loans
Current		35,680	37,788
30 to 89 Days Past Due		298	179
90 Days or More Past Due		58	51
Total past due		356	230
Loans held for investment		36,036	38,018
Commercial mortgage | Commercial Loans
Aging of loans
Current		16,896	16,858
30 to 89 Days Past Due		45	34
90 Days or More Past Due		2	3
Total past due		47	37
Loans held for investment		16,943	16,895
Commercial and industrial | Commercial Loans
Aging of loans
Current		30,645	27,241
30 to 89 Days Past Due		158	37
90 Days or More Past Due		49	61
Total past due		207	98
Loans held for investment		30,852	27,339
Construction | Commercial Loans
Aging of loans
Current		1,582	1,511
30 to 89 Days Past Due		1	0
90 Days or More Past Due		0	0
Total past due		1	0
Loans held for investment		1,583	1,511
Other Consumer Loans [Member] | Consumer Loans
Aging of loans
Current		4,318	4,400
30 to 89 Days Past Due		36	33
90 Days or More Past Due		18	17
Total past due		54	50
Loans held for investment		$ 4,372	$ 4,450

[1] Includes $279 million and $320 million at March 31, 2020 and December 31, 2019, respectively, for net unamortized (discounts) and premiums and deferred (fees) and costs.Accrued interest receivable on loans held for investment and securities totaled $469 million at March 31, 2020 and is included in the other assets on the consolidated balance sheet.