Loans - Status of Consumer Loan Portfolio (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More		$ 15	$ 18
Total loans		67,338	72,563	$ 69,588
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		19,111	19,030
Nonaccrual Loans		474	481
Accruing Loans Contractually Past Due 90 days or More		14	17
Total loans		19,599	19,528
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		16,917	16,859
Nonaccrual Loans	[1],[2],[3]	408	414
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		17,325	17,273	17,219
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		1,073	1,124
Nonaccrual Loans	[1],[3]	66	67
Accruing Loans Contractually Past Due 90 days or More		0	0
Total loans		1,139	1,191	1,344
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		762	712
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		8	9
Total loans		770	721	646
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		359	335
Nonaccrual Loans		0	0
Accruing Loans Contractually Past Due 90 days or More		6	8
Total loans		$ 365	$ 343	$ 383

[1] At March 31, 2018 and December 31, 2017, nonaccrual consumer mortgage loans held for investment include $362 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 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.