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Variable Interest Entities and Securitizations - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Amortization method qualified affordable housing investments, amortization	$ 428	$ 417
Affordable housing tax credits	47	$ 516
Amortization method qualified affordable housing investments	4,500		$ 4,400
Qualified affordable housing investments, commitment	1,500		1,500
Carrying Amount of Assets	421,883		390,365
VIE, reporting entity involvement, maximum loss exposure	5,361		5,413
Affordable housing entities
Variable Interest Entity [Line Items]
VIE, reporting entity involvement, maximum loss exposure	4,582		4,559
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
VIE, reporting entity involvement, maximum loss exposure	0		0
Other
Variable Interest Entity [Line Items]
VIE, reporting entity involvement, maximum loss exposure	466		502
Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,104		5,127
Unconsolidated | Affordable housing entities
Variable Interest Entity [Line Items]
Total assets of the unconsolidated VIE investment funds	10,800		10,900
Carrying Amount of Assets	4,582		4,559
Unconsolidated | Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0		0
Unconsolidated | Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets	466		502
Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	31,514		35,519
Consolidated | Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	243		236
Consolidated | Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,014		1,889
Consolidated | Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets	$ 0		$ 0

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Amount of affordable housing tax credits and other tax benefits recognized.

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