Loans - Status of Consumer Loan Portfolio (Detail) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More		$ 17	$ 18
Total loans		66,399	72,563	$ 68,063
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		19,072	19,030
Nonaccrual Loans		468	481
Accruing Loans Contractually Past Due 90 days or More		16	17
Total loans		19,556	19,528
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		16,921	16,859
Nonaccrual Loans	[1],[2],[3]	405	414
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		17,326	17,273	17,119
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		1,023	1,124
Nonaccrual Loans	[1],[3]	63	67
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		1,086	1,191	1,285
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		830	712
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		11	9
Total loans		841	721	647
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		298	335
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		5	8
Total loans		$ 303	$ 343	$ 424

[1] At June 30, 2018 and December 31, 2017, nonaccrual consumer mortgage loans held for investment include $348 million and $360 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 is 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.