Loans and Allowance for Credit Losses - Additional Detail of Allowance for Credit Losses and Related Loan Balances by Portfolio Type (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Allowance Balance at End of Period
Loans individually evaluated for impairment	$ 26		$ 32
TDRs collectively evaluated for impairment	482		520
Other loans collectively evaluated for impairment	3,804		3,815
Loans acquired with deteriorated credit quality	137		170
Total allowance for credit losses	4,449	4,497	4,537	4,612	4,708	4,733
Loan balance at end of period
Loans individually evaluated for impairment	502		496
TDRs collectively evaluated for impairment	6,300		6,243
Other loans collectively evaluated for impairment	233,476		224,557
Loans acquired with deteriorated credit quality	3,596		3,939
Total loans	236,426		226,773
Total loans	243,874		235,235
Commercial [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	19		15
TDRs collectively evaluated for impairment	15		19
Other loans collectively evaluated for impairment	1,077		1,041
Loans acquired with deteriorated credit quality
Total allowance for credit losses	1,111	1,091	1,075	1,023	1,012	1,051
Loan balance at end of period
Loans individually evaluated for impairment	273		197
TDRs collectively evaluated for impairment	133		155
Other loans collectively evaluated for impairment	77,047		69,680
Loans acquired with deteriorated credit quality	1		1
Total loans	77,454		70,033
Commercial Real Estate [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	7		17
TDRs collectively evaluated for impairment	17		26
Other loans collectively evaluated for impairment	669		700
Loans acquired with deteriorated credit quality	32		33
Total allowance for credit losses	725	742	776	777	798	857
Loan balance at end of period
Loans individually evaluated for impairment	159		237
TDRs collectively evaluated for impairment	301		358
Other loans collectively evaluated for impairment	40,206		39,129
Loans acquired with deteriorated credit quality	131		161
Total loans	40,797		39,885
Residential Mortgages [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	326		329
Other loans collectively evaluated for impairment	522		546
Loans acquired with deteriorated credit quality
Total allowance for credit losses	848	862	875	921	926	935
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	5,260		5,064
Other loans collectively evaluated for impairment	46,704		46,090
Loans acquired with deteriorated credit quality	1		2
Total loans	51,965		51,156
Credit Card [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	69		87
Other loans collectively evaluated for impairment	805		797
Loans acquired with deteriorated credit quality
Total allowance for credit losses	874	884	884	874	895	863
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	272		310
Other loans collectively evaluated for impairment	17,370		17,711
Loans acquired with deteriorated credit quality
Total loans	17,642		18,021
Other Retail [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	52		55
Other loans collectively evaluated for impairment	727		726
Loans acquired with deteriorated credit quality
Total allowance for credit losses	779	785	781	838	854	848
Loan balance at end of period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	252		269
Other loans collectively evaluated for impairment	48,316		47,409
Loans acquired with deteriorated credit quality
Total loans	48,568		47,678
Total Loans, Excluding Covered Loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment	26		32
TDRs collectively evaluated for impairment	479		516
Other loans collectively evaluated for impairment	3,800		3,810
Loans acquired with deteriorated credit quality	32		33
Total allowance for credit losses	4,337	4,364	4,391	4,433	4,485	4,554
Loan balance at end of period
Loans individually evaluated for impairment	432		434
TDRs collectively evaluated for impairment	6,218		6,156
Other loans collectively evaluated for impairment	229,643		220,019
Loans acquired with deteriorated credit quality	133		164
Total loans	236,426		226,773
Covered Loans [Member]
Allowance Balance at End of Period
Loans individually evaluated for impairment
TDRs collectively evaluated for impairment	3		4
Other loans collectively evaluated for impairment	4		5
Loans acquired with deteriorated credit quality	105		137
Total allowance for credit losses	112	133	146	179	223	179
Loan balance at end of period
Loans individually evaluated for impairment	70		62
TDRs collectively evaluated for impairment	82		87
Other loans collectively evaluated for impairment	3,833		4,538
Loans acquired with deteriorated credit quality	3,463		3,775
Total loans	$ 7,448		$ 8,462