Variable Interest Entities and Securitizations - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Variable Interest Entity [Line Items]
Funded HELOCs advances	$ 30		$ 30
Unfunded commitment on residual interests on trusts	5		6
Maximum exposure to loss	5,230		4,782
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	553		582
Amortization Method Qualified Affordable Housing Project Investments, Amortization	295	$ 257
Affordable Housing Tax Credits And Other Tax Benefits, Amount	336	$ 387
Amortization Method Qualified Affordable Housing Project Investments	3,800		3,500
Qualified Affordable Housing Project Investments, Commitment	1,300		1,300
Carrying amounts of assets, unconsolidated	4,153		4,120
VIEs consolidated assets	$ 32,505		35,152
Minimum
Variable Interest Entity [Line Items]
Affordable Housing Tax Credits Commitment, Year to be Paid	2016
Maximum
Variable Interest Entity [Line Items]
Affordable Housing Tax Credits Commitment, Year to be Paid	2019
Affordable housing entities
Variable Interest Entity [Line Items]
Maximum exposure to loss	$ 3,884		3,852
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	527		555
Carrying amounts of assets, unconsolidated	3,884		3,852
Total assets of the unconsolidated VIE investment funds	11,500		11,400
VIEs consolidated assets	173		0
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Maximum exposure to loss	0		0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0
Carrying amounts of assets, unconsolidated	0		0
VIEs consolidated assets	789		352
Other
Variable Interest Entity [Line Items]
Maximum exposure to loss	64		57
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0
Carrying amounts of assets, unconsolidated	64		57
VIEs consolidated assets	0		0
GreenPoint Manufactured Housing
Variable Interest Entity [Line Items]
Maximum exposure to loss	420
Qualitative and Quantitative information, transferor's continuing involvement, maximum credit exposure, carrying amount	12		13
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	7		8
Variable Interest Entity, Not Primary Beneficiary | Option- ARM
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	1,563		1,754
Unpaid principal balance of securitization trusts	1,616		1,814
Variable Interest Entity, Not Primary Beneficiary | GreenPoint HELOCs
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	60		74
Unpaid principal balance of securitization trusts	54		68
Variable Interest Entity, Not Primary Beneficiary | GreenPoint Manufactured Housing
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	719		789
Unpaid principal balance of securitization trusts	724		794
Maximum exposure to loss	420
Letters of credit funded	$ 83		$ 76