Certain Transfers of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Loans and Leases Receivable, Gain (Loss) on Sales, Net		$ 45		$ 47
Loans and Leases Receivable, Net Amount		156,756		156,756		$ 150,224
Total liabilities		200,879		200,879		191,263
Long-term Debt	[1]	20,369		20,369		15,072
Debt Securities, Trading, and Equity Securities, FV-NI	[2]	7,104		7,104		5,506
Amortization of Intangible Assets	[3]			9	$ 13
Variable Interest Entity, Not Primary Beneficiary [Member]
Investment Tax Credit		25	$ 23	64	62
Amortization of Intangible Assets		21	19	53	49
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt		143		143		161
Residential Mortgage [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		108	46	223	53
Commercial and Corporate Loans [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		9	$ 8	28	$ 22
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Loans and Leases Receivable, Net Amount		147		147		165
Long-term Debt		$ 143		$ 143		$ 161
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		98.00%		98.00%		98.00%
Total Return Swap [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Derivative Asset, Notional Amount		$ 2,500		$ 2,500		$ 2,000
Debt Securities, Trading, and Equity Securities, FV-NI		$ 2,500		$ 2,500		$ 2,000
Death, Disability, Bankruptcy [Member] | Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		100.00%		100.00%

[1] Includes debt of consolidated VIEs of $143 million and $161 million at September 30, 2019 and December 31, 2018, respectively.

[2] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,284 million and $1,442 million at September 30, 2019 and December 31, 2018, respectively.

[3] Does not include expense associated with community development investments. See Note 11, “Certain Transfers of Financial Assets and Variable Interest Entities,” for additional information.