Credit Quality (Summary of Transactions in the ALLL by Portfolio segment) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	[1],[2]	$ 1,196		$ 1,253
Losses charged-off		(103)		(107)
Recoveries of losses previously charged- off		22		18
Provision for (benefit from) loan and lease losses		23		74
Balance, end of period		1,138	[2],[3]	1,238
Commercial Portfolio Segment
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	[1]	753		831
Losses charged-off		(35)		(46)
Recoveries of losses previously charged- off		6		4
Provision for (benefit from) loan and lease losses		(11)		37
Balance, end of period		713	[3]	826
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	[1]	89		96
Losses charged-off		(4)		(6)
Recoveries of losses previously charged- off		1		1
Provision for (benefit from) loan and lease losses		3		5
Balance, end of period		89	[3]	96
Consumer Portfolio Segment
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	[1]	234		214
Losses charged-off		(64)		(55)
Recoveries of losses previously charged- off		15		13
Provision for (benefit from) loan and lease losses		37		32
Balance, end of period		222	[3]	204
Unallocated
Financing Receivable, Allowance for Credit Losses
Balance, beginning of period	[1]	120		112
Losses charged-off		0		0
Recoveries of losses previously charged- off		0		0
Provision for (benefit from) loan and lease losses		(6)		0
Balance, end of period		$ 114	[3]	$ 112

[1] Includes $ 1 related to leveraged leases at December 31, 2017 .

[2] Includes $ 66 and $ 62 of other short-term investments , $ 1,135 and $ 1,297 of portfolio loans and leases, $ (6) and $ (6) of ALLL, $ 6 and $ 7 of other assets, $ 2 and $ 2 of other liabilities, and $ 1,031 and $ 1,190 of long-term debt from consolidated VIEs that are included in their respe ctive captions above at March 31, 2018 and December 31, 2017 , respectively. For further information refer to Note 9 .

[3] Includes $ 1 related to leveraged leases at March 31, 2018 .