Loans - Status of Consumer Loan Portfolio (Detail) - USD ($) $ in Millions	Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Credit Quality Indicator [Line Items]
Nonaccrual Loans	$ 664		$ 539
Accruing Loans Contractually Past Due 90 days or More	30		21
Total loans	68,553		68,978	$ 72,563
Consumer Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Performing Loans	19,886		19,220
Nonaccrual Loans	427		396
Accruing Loans Contractually Past Due 90 days or More	29		20
Total loans	20,342		19,636
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Performing Loans	17,420		17,042
Nonaccrual Loans	381		341
Accruing Loans Contractually Past Due 90 days or More	0		0
Total loans	17,801		17,383	17,273
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Performing Loans	807		927
Nonaccrual Loans	46		55
Accruing Loans Contractually Past Due 90 days or More	0		0
Total loans	853	[1]	982	1,191
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Performing Loans	1,381		1,005
Nonaccrual Loans	0		0
Accruing Loans Contractually Past Due 90 days or More	24		14
Total loans	1,405	[2]	1,019	721
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Performing Loans	278		246
Nonaccrual Loans	0		0
Accruing Loans Contractually Past Due 90 days or More	5		6
Total loans	$ 283		$ 252	$ 343

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

[2] As credit card receivables do not have stated maturities, the table reflects an average estimate based on historical payment patterns.