Loans - Status of Consumer Loan Portfolio (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Accruing Loans Contractually Past Due 90 days or More		$ 18		$ 18
Total loans		72,563		73,875	$ 82,917
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		19,030		19,132
Nonaccrual Loans		481		510
Accruing Loans Contractually Past Due 90 days or More		17		17
Total loans		19,528		19,659
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		16,859		16,746
Nonaccrual Loans	[1],[2],[3]	414		435
Accruing Loans Contractually Past Due 90 days or More		0		0
Total loans		17,273		17,181	17,758
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		1,124		1,333
Nonaccrual Loans	[1],[3]	67		75
Accruing Loans Contractually Past Due 90 days or More		0		0
Total loans		1,191	[4]	1,408	1,600
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		712		678
Nonaccrual Loans		0		0
Accruing Loans Contractually Past Due 90 days or More		9		10
Total loans		721	[5]	688	699
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans		335		375
Nonaccrual Loans		0		0
Accruing Loans Contractually Past Due 90 days or More		8		7
Total loans		$ 343		$ 382	$ 407

[1] At December 31, 2017 and 2016, nonaccrual consumer mortgage loans held for investment include $360 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.

[4] Home equity mortgage maturities reflect estimates based on historical payment patterns.

[5] As credit card receivables do not have stated maturities, the table reflects estimates based on historical payment patterns.