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Variable Interest Entities and Securitizations - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Amortization method qualified affordable housing investments, amortization	$ 285	$ 279
Affordable housing tax credits	622	$ 355
Amortization method qualified affordable housing investments	4,500		$ 4,400
Qualified affordable housing investments, commitment	1,500		1,500
Carrying Amount of Assets	421,296		390,365
VIE, reporting entity involvement, maximum loss exposure	5,348		5,413
Affordable housing entities
Variable Interest Entity [Line Items]
VIE, reporting entity involvement, maximum loss exposure	4,553		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	476		502
Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,085		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	4,553		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	476		502
Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	30,404		35,519
Consolidated | Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	248		236
Consolidated | Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,030		1,889
Consolidated | Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets	$ 0		$ 0

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