Long-Term Debt (Long-Term Debt - Additional Information) (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2017	Dec. 31, 2016
Debt Instrument
Face amount of notes issued or redeemed		$ 700
Maturity date(s) Start		Jun. 15, 2017
Maturity date(s) End		Jun. 15, 2022
Long-term debt oustanding	[1]	$ 14,039	$ 14,388
Variable Interest Entity, Primary Beneficiary
Debt Instrument
Long-term debt oustanding		1,491	$ 1,094
Automobile Loan Securitization
Debt Instrument
Long-term debt oustanding		750
Long-term debt retained		261
Automobile Loan Securitization | Variable Interest Entity, Primary Beneficiary
Debt Instrument
Face amount of notes issued or redeemed		1,000
Carry value of automobile loans securitized		$ 1,100

[1] Includes $ 116 and $ 85 of cash and due from banks, $ 1,532 and $ 1,216 of portfolio loans and leases , $ (8) and $ (26) of ALLL, $ 9 and $ 9 of other assets, $ 3 and $ 3 of other liabilities , and $ 1,491 and $ 1,094 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2017 and December 31, 2016 , respectively. For further information refer to Note 11 .