Credit Quality (Summary of the ALLL and Related Loans and Leases Classified by Portfolio Segment) (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2018		Jun. 30, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	$ 1,091	[1]	$ 1,077	$ 1,196	[1]	$ 1,205	$ 1,226	$ 1,253
Loans measured at fair value on a recurring basis	1,010					$ 848
Portfolio loans and leases	93,271			91,833
Residential Mortgage Loans
Financing Receivable, Allowance for Credit Losses
Loans measured at fair value on a recurring basis	172			137
Leveraged leases
Financing Receivable, Allowance for Credit Losses
Allowance for loan and lease losses	1			1
Portfolio loans and leases	$ 638			$ 674

[1] Includes $ 41 and $ 62 of other short-term investments , $ 793 and $ 1,297 of portfolio loans and leases, $ (4) and $ (6) of ALLL, $ 5 and $ 7 of other assets, $ 1 and $ 2 of other liabilities, and $ 710 and $ 1,190 of long-term debt from consolidated VIEs that are included in their respe ctive captions above at September 30, 2018 and December 31, 2017 , respectively. For further information refer to Note 10 .