Loans - Delinquency Ratio for Consumer Loan (Detail) - Consumer Loans [Member] - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 385	$ 486
Delinquency Ratio		1.96%	2.48%
Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans	[1],[2]	$ 329	$ 425
Delinquency Ratio	[1],[2]	1.89%	2.46%
Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans	[1],[2]	$ 31	$ 39
Delinquency Ratio	[1],[2]	3.02%	3.27%
Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 18	$ 12
Delinquency Ratio		1.98%	1.66%
Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 7	$ 10
Delinquency Ratio		2.20%	2.48%

[1] At September 30, 2018 and December 31, 2017, consumer mortgage loan delinquency includes $263 million and $342 million, respectively, of loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell, including $1 million and $1 million, respectively, relating to loans held for sale.

[2] At September 30, 2018 and December 31, 2017, consumer mortgage loans and loans held for sale include $157 million and $159 million, respectively, of loans that were in the process of foreclosure.