Loans - Delinquency Ratio for Consumer Loan (Detail) - Consumer Loans [Member] - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 486	$ 836
Delinquency Ratio		2.48%	4.05%
Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans	[1],[2]	$ 425	$ 765
Delinquency Ratio	[1],[2]	2.46%	4.23%
Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans	[1],[2]	$ 39	$ 46
Delinquency Ratio	[1],[2]	3.27%	3.26%
Credit Cards [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 12	$ 14
Delinquency Ratio		1.66%	2.03%
Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Delinquent Loans		$ 10	$ 11
Delinquency Ratio		2.48%	2.43%

[1] At December 31, 2017 and 2016, consumer mortgage loan delinquency includes $342 million and $711 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 $358 million, respectively, relating to loans held for sale.

[2] At December 31, 2017 and 2016, consumer mortgage loans and loans held for sale include $159 million and $474 million, respectively, of loans that were in the process of foreclosure.