Certain Transfers of Financial Assets and Variable Interest Entities - Additional Information (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows Between Transferor and Transferee, Receipts on Transferor's Interest in Transferred Financial Assets, Other		$ 11	$ 12	$ 19
Assets		205,962	204,875
Total liabilities		180,808	181,257
Long-term Debt	[1],[2]	9,785	11,748
Derivative Asset, Notional Amount		143,238	127,456
Trading Securities	[3]	5,093	6,067
Other Assets		8,949	6,405
Affordable Housing Tax Credits and Other Tax Benefits, Amount		108	92	68
Amortization Method Qualified Affordable Housing Project Investments, Amortization		109	87	66
Amortization of Intangible Assets	[4]	20	9
Amortization		75	49	40
Variable Interest Entity, Not Primary Beneficiary [Member] | Community Development Investments [Member]
Investment Tax Credit		90	64	53
Amortization of Intangible Assets		70	46	35
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt		189	222
Residential Mortgage [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		213	331	$ 232
Transferor's Interests in Transferred Financial Assets, Fair Value		22	30
Assets		147	203
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		22	30
Commercial and Corporate Loans [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Loans and Leases Receivable, Gain (Loss) on Sales, Net		37
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Loans Receivable, Net		192	225
Long-term Debt		$ 189	$ 222
Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		98.00%	98.00%
Total Return Swap [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Derivative Asset, Notional Amount		$ 1,700	$ 2,100
Trading Securities		1,700	2,100
Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Assets		2,300	1,700
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		643	562
Real Estate Variable Interest Entity Borrowings		278	200
Limited Partner [Member] | Community Development Investments [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Other Assets		1,053	780
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		1,391	1,076
Loans Issued by the Company to the Limited Partnerships		$ 350	$ 306
Death, Disability, Bankruptcy [Member] | Student Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Maximum [Member]
Government Guarantee Percent		100.00%

[1] Includes $530 million and $963 million of long-term debt measured at fair value at December 31, 2017 and 2016, respectively.

[2] Includes debt of consolidated VIEs of $189 million and $222 million at December 31, 2017 and December 31, 2016, respectively.

[3] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,086 million and $1,437 million at December 31, 2017 and December 31, 2016, respectively.

[4] Does not include expense associated with non-qualified community development investments. See Note 10, "Certain Transfers of Financial Assets and Variable Interest Entities," for additional information.