Certain Transfers of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		$ 2	$ 3
Total assets		205,642			$ 204,875
Total liabilities		182,158			181,257
Long-term Debt	[1]	10,496			11,748
Potential loss on securitization of loans		448
Derivative Asset, Notional Amount		$ 119,513			133,395
Document Period End Date		Mar. 31, 2017
Trading assets	[2]	$ 6,007			6,067
Other Assets		6,700			6,405
Affordable Housing Tax Credits and Other Tax Benefits, Amount		25	19
Amortization Method Qualified Affordable Housing Project Investments, Amortization		24	19
Amortization of Intangible Assets	[3]	5	2
Amortization		13	10
Affordable Housing Investment [Member]
Properties sold, carrying value		1
Gain (Loss) on Sale of Properties		4
Variable Interest Entity, Not Primary Beneficiary [Member] | Community Development Investments [Member]
Investment Tax Credit		17	13
Amortization of Intangible Assets		12	9
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt		214			222
Residential Mortgage [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		(4)	$ 69
Transferor's Interests in Transferred Financial Assets, Fair Value		29			30
Total assets		196			203
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		29			30
Commercial and Corporate Loans [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		9
Total assets					185
Total liabilities					159
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Loans Receivable, Net		216			225
Long-term Debt		$ 214			222
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		100.00%
Total Return Swap [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Derivative Asset, Notional Amount		$ 2,100			2,100
Trading assets		2,100			2,100
Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Total assets		1,900			1,700
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		612			562
Real Estate Variable Interest Entity Borrowings		217			200
Limited Partner [Member] | Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Other Assets		834			780
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		1,150			1,076
Loans issued by the Company to the limited partnerships		$ 338			$ 306
Consumer Portfolio Segment [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member]
Proceeds from Securitizations of Consumer Loans				$ 1,000

[1] Includes debt of consolidated VIEs of $214 million and $222 million at March 31, 2017 and December 31, 2016, respectively.

[2] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,229 million and $1,437 million at March 31, 2017 and December 31, 2016, respectively.

[3] Does not include expense associated with non-qualified community development investments. See Note 9, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.