Loans and Allowance for Credit Losses - Additional Detail of Allowance for Credit Losses and Related Loan Balances by Portfolio Class (Detail) - USD ($) $ in Millions	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Allowance Balance at End of Period
Loans individually evaluated for impairment	$ 36		$ 54
TDRs collectively evaluated for impairment	254		282
Other loans collectively evaluated for impairment	4,050		3,982
Loans acquired with deteriorated credit quality	37		39
Total allowance for credit losses	4,377	$ 4,366	4,357	$ 4,329	$ 4,320	$ 4,306
Loan Balance at End of Period
Loans individually evaluated for impairment	483		693
TDRs collectively evaluated for impairment	4,523		4,399
Other loans collectively evaluated for impairment	270,084		265,728
Loans acquired with deteriorated credit quality	2,193		2,387
Total loans	273,846		269,371
Total loans	277,283		273,207
Commercial [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	33		50
TDRs collectively evaluated for impairment	14		12
Other loans collectively evaluated for impairment	1,348		1,388
Total allowance for credit losses	1,395	1,429	1,450	1,473	1,441	1,287
Loan Balance at End of Period
Loans individually evaluated for impairment	421		623
TDRs collectively evaluated for impairment	166		145
Other loans collectively evaluated for impairment	96,249		92,611
Loans acquired with deteriorated credit quality			7
Total loans	96,836		93,386
Commercial Real Estate [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	3		4
TDRs collectively evaluated for impairment	4		4
Other loans collectively evaluated for impairment	844		798
Loans acquired with deteriorated credit quality	5		6
Total allowance for credit losses	856	842	812	748	734	724
Loan Balance at End of Period
Loans individually evaluated for impairment	62		70
TDRs collectively evaluated for impairment	146		146
Other loans collectively evaluated for impairment	41,622		42,751
Loans acquired with deteriorated credit quality	78		131
Total loans	41,908		43,098
Residential Mortgages [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	151		180
Other loans collectively evaluated for impairment	304		330
Total allowance for credit losses	455	485	510	544	556	631
Loan Balance at End of Period
TDRs collectively evaluated for impairment	3,780		3,678
Other loans collectively evaluated for impairment	55,016		53,595
Loans acquired with deteriorated credit quality			1
Total loans	58,796		57,274
Other Retail [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	20		20
Other loans collectively evaluated for impairment	628		597
Total allowance for credit losses	648	622	617	643	678	743
Loan Balance at End of Period
TDRs collectively evaluated for impairment	168		173
Other loans collectively evaluated for impairment	55,276		53,691
Loans acquired with deteriorated credit quality	1
Total loans	55,445		53,864
Credit Card [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	64		65
Other loans collectively evaluated for impairment	926		869
Total allowance for credit losses	990	955	934	884	875	883
Loan Balance at End of Period
TDRs collectively evaluated for impairment	230		222
Other loans collectively evaluated for impairment	20,631		21,527
Total loans	20,861		21,749
Total Loans, Excluding Covered Loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	36		54
TDRs collectively evaluated for impairment	253		281
Other loans collectively evaluated for impairment	4,050		3,982
Loans acquired with deteriorated credit quality	5		6
Total allowance for credit losses	4,344	4,333	4,323	4,292	4,284	4,268
Loan Balance at End of Period
Loans individually evaluated for impairment	483		693
TDRs collectively evaluated for impairment	4,490		4,364
Other loans collectively evaluated for impairment	268,794		264,175
Loans acquired with deteriorated credit quality	79		139
Total loans	273,846		269,371
Covered Loans [Member]
Allowance Balance at End of Period
TDRs collectively evaluated for impairment	1		1
Loans acquired with deteriorated credit quality	32		33
Total allowance for credit losses	33	$ 33	34	$ 37	$ 36	$ 38
Loan Balance at End of Period
TDRs collectively evaluated for impairment	33		35
Other loans collectively evaluated for impairment	1,290		1,553
Loans acquired with deteriorated credit quality	2,114		2,248
Total loans	$ 3,437		$ 3,836