Loans - Delinquency Ratio for Consumer Loan (Detail) - USD ($) $ in Millions		Dec. 31, 2020		Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans		$ 62,088		$ 68,553
Residential Mortgage Loan Delinquency Carried At Lower Of Amortized Cost Or Fair Value Less Cost To Sell		281		256
Consumer Loans [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		4,666
2019		2,566
2018		1,465
2017		1,694
2016		1,985
Prior		6,991
Revolving Loans		1,122
Total loans		20,489		20,342
Mortgage Loans in Process of Foreclosure, Amount		109		142
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		4,529
2019		2,476
2018		1,431
2017		1,658
2016		1,930
Prior		6,353
Revolving Loans		0
Total loans		18,377		17,801
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		50
2019		51
2018		34
2017		35
2016		47
Prior		510
Revolving Loans		0
Total loans		727	[1]	853
Consumer Loans [Member] | Credit Cards [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		0
2019		0
2018		0
2017		0
2016		0
Prior		0
Revolving Loans		1,066
Total loans		1,066	[2]	1,405
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		87
2019		39
2018		0
2017		1
2016		8
Prior		128
Revolving Loans		56
Total loans	[3]	319		283
Consumer Loans [Member] | Contractual Delinquency, 60 Days or More Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		4
2019		16
2018		13
2017		25
2016		19
Prior		358
Revolving Loans		30
Total loans		465		416
Consumer Loans [Member] | Contractual Delinquency, 60 Days or More Past Due [Member] | Residential Mortgage [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	[4],[5]	3
2019	[4],[5]	15
2018	[4],[5]	13
2017	[4],[5]	25
2016	[4],[5]	19
Prior	[4],[5]	329
Revolving Loans	[4],[5]	0
Total loans	[4],[5]	404		350
Consumer Loans [Member] | Contractual Delinquency, 60 Days or More Past Due [Member] | Home Equity Mortgages [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020	[4],[5]	0
2019	[4],[5]	0
2018	[4],[5]	0
2017	[4],[5]	0
2016	[4],[5]	0
Prior	[4],[5]	25
Revolving Loans	[4],[5]	0
Total loans	[4],[5]	25		25
Consumer Loans [Member] | Contractual Delinquency, 60 Days or More Past Due [Member] | Credit Cards [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020
2019
2018
2017
2016
Prior
Revolving Loans		28
Total loans		28		34
Consumer Loans [Member] | Contractual Delinquency, 60 Days or More Past Due [Member] | Other consumer [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
2020		1
2019		1
2018		0
2017		0
2016		0
Prior		4
Revolving Loans		2
Total loans		$ 8		$ 7

[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

[3] Includes certain student loans that we have elected to designate under the fair value option and are therefore carried at fair value, which totaled $32 million at December 31, 2020. See Note 16, "Fair Value Option," for further details.

[4] At December 31, 2020 and 2019, consumer mortgage loans include $109 million and $142 million, respectively, of loans that were in the process of foreclosure.

[5] At December 31, 2020 and 2019, consumer mortgage loan delinquency includes $281 million and $256 million, respectively, of loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell.