Variable Interest Entities and Securitizations - External Debt and Receivable Balances of Securitization Programs (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity, Primary Beneficiary
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, non-mortgage	$ 11,624	$ 10,289
Receivables in the trust, non-mortgage	36,545	39,548
Cash balance of spread or reserve accounts, non-mortgage	0	3
Variable Interest Entity, Not Primary Beneficiary | Option ARM
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, mortgage	2,026	2,320
Receivables in the trust, mortgage	2,094	2,399
Cash balance of spread or reserve accounts, mortgage	8	8
Variable Interest Entity, Not Primary Beneficiary | GreenPoint HELOCs
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, mortgage	95	122
Receivables in the trust, mortgage	89	116
Variable Interest Entity, Not Primary Beneficiary | GreenPoint Manufactured Housing
Qualitative and Quantitative Information, Transferor's Continuing Involvement [Line Items]
Securities held by third-party investors, mortgage	887	994
Receivables in the trust, mortgage	893	1,000
Cash balance of spread or reserve accounts, mortgage	$ 143	$ 144