Variable Interest Entities and Securitizations - Additional Information (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Funded HELOCs advances	$ 30,000,000	$ 29,000,000
Unfunded commitment on residual interests on trusts	7,000,000	7,000,000
Carrying Amount of Assets, Unconsolidated	3,534,000,000	3,264,000,000
Maximum exposure to loss	4,189,000,000	3,767,000,000
VIEs consolidated assets	37,373,000,000	40,812,000,000
Carrying amount of other VIE assets and liabilities	172,000,000	204,000,000
Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Unconsolidated	3,250,000,000	2,969,000,000
Maximum exposure to loss	3,250,000,000	2,969,000,000
Total assets of the unconsolidated VIE investment funds	10,000,000,000	9,800,000,000
VIEs consolidated assets	0	0
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Unconsolidated	1,000,000	1,000,000
Maximum exposure to loss	1,000,000	1,000,000
VIEs consolidated assets	391,000,000	389,000,000
Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets, Unconsolidated	80,000,000	95,000,000
Maximum exposure to loss	80,000,000	95,000,000
VIEs consolidated assets	6,000,000	1,000,000
Retained interest in the trust	80,000,000	93,000,000
Maximum loss exposure to royalty payment	80,000,000	93,000,000
Variable Interest Entity, Not Primary Beneficiary | Option ARM
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	2,094,000,000	2,320,000,000
Unpaid principal balance of securitization trusts	2,165,000,000	2,399,000,000
Variable Interest Entity, Not Primary Beneficiary | GreenPoint HELOCs
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	102,000,000	122,000,000
Unpaid principal balance of securitization trusts	97,000,000	116,000,000
Variable Interest Entity, Not Primary Beneficiary | GreenPoint Manufactured Housing
Variable Interest Entity [Line Items]
Securities held by third-party investors, mortgage	912,000,000	994,000,000
Unpaid principal balance of securitization trusts	918,000,000	1,000,000,000
Maximum exposure to loss	$ 420,000,000