Asset Quality - Post-Modification Outstanding Recorded Investment by Concession Type for Our Commercial Accruing and Nonaccruing TDRs (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Modifications [Line Items]
Total commercial and consumer TDRs	$ 71	$ 83	$ 79
Total loans	86,038	59,876	57,381
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Interest rate reduction			2
Forgiveness of principal			0
Other			19
Total			21
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Interest rate reduction			29
Forgiveness of principal			1
Other			28
Total			$ 58
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Total loans		15,604
Consumer Loans [Member] | Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Interest rate reduction	10	19
Forgiveness of principal	3	4
Other	21	17
Total	34	40
Total loans	24,129
Commercial Loans [Member] | Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
Interest rate reduction	14	43
Forgiveness of principal	0	0
Other	23	0
Total	37	43
Total loans	$ 61,909	$ 44,272