Loans - Status of Consumer Loan Portfolio (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More		$ 19	$ 18
Total loans		67,593	73,875	$ 77,625
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		18,947	19,132
Nonaccrual Loans		504	510
Accruing Loans Contractually Past Due 90 days or More		14	17
Total loans		19,465	19,659
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		16,761	16,746
Nonaccrual Loans	[1],[2],[3]	435	435
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		17,196	17,181	17,091
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		1,165	1,333
Nonaccrual Loans	[1],[3]	69	75
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		1,234	1,408	1,454
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		648	678
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		8	10
Total loans		656	688	668
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		373	375
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		6	7
Total loans		$ 379	$ 382	$ 380

[1] At September 30, 2017 and December 31, 2016, nonaccrual consumer mortgage loans held for investment include $378 million and $382 million, respectively, of loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell.

[2] Nonaccrual consumer mortgage loans for all periods does not include guaranteed loans purchased from the Government National Mortgage Association. Repayment of these loans are predominantly insured by the Federal Housing Administration and as such, these loans have different risk characteristics from the rest of our consumer loan portfolio.

[3] Nonaccrual consumer mortgage loans held for investment include all loans which are 90 or more days contractually delinquent as well as loans discharged under Chapter 7 bankruptcy and not re-affirmed and second lien loans where the first lien loan that we own or service is 90 or more days contractually delinquent.