Credit Quality (Summary of Subsequent Defaults) (Detail) $ in Millions		12 Months Ended
		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Modifications
Number of contracts	[1]	1,918	2,124	2,346
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 39	$ 42	$ 87
Commercial Portfolio Segment | Commercial and Industrial Loans
Financing Receivable, Modifications
Number of contracts	[1]	8	7	11
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 5	$ 11	$ 36
Commercial Portfolio Segment | Commercial Mortgage Loans, Owner-Occupied
Financing Receivable, Modifications
Number of contracts	[1]		3	3
Recorded Investment in Loans Modified in a TDR During the Period	[1]		$ 1	$ 4
Commercial Portfolio Segment | Commercial Mortgage Loans, Nonowner-Occupied
Financing Receivable, Modifications
Number of contracts	[1]	2		2
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 0		$ 1
Commercial Portfolio Segment | Commercial leases
Financing Receivable, Modifications
Number of contracts	[1]	2
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 1
Residential Mortgage Loans
Financing Receivable, Modifications
Number of contracts	[1]	172	156	235
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 25	$ 21	$ 32
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications
Number of contracts	[1]	17	15	30
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 1	$ 1	$ 2
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications
Number of contracts	[1]	2	8	6
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 0	$ 0	$ 0
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications
Number of contracts	[1]	1,715	1,935	2,059
Recorded Investment in Loans Modified in a TDR During the Period	[1]	$ 7	$ 8	$ 12

[1] (a) Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality .