Variable Interest Entities and Securitizations - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Variable Interest Entity [Line Items]
Funded HELOCs advances	$ 30		$ 30
Unfunded commitment on residual interests on trusts	5		5
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	1,335		1,120
Amortization Method Qualified Affordable Housing Project Investments, Amortization	230	$ 196
Affordable Housing Tax Credits And Other Tax Benefits, Amount	238	$ 228
Amortization Method Qualified Affordable Housing Project Investments	4,000		3,800
Qualified Affordable Housing Project Investments, Commitment	1,400		1,200
Variable Interest Entity, Consolidated, Carrying Amount, Assets	30,248		34,651
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	4,664		4,250
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 5,619		5,325
Minimum
Variable Interest Entity [Line Items]
Affordable Housing Tax Credits Commitment, Year to be Paid	2017
Maximum
Variable Interest Entity [Line Items]
Affordable Housing Tax Credits Commitment, Year to be Paid	2019
Affordable housing entities
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	$ 1,266		1,093
Total assets of the unconsolidated VIE investment funds	11,400		11,500
Variable Interest Entity, Consolidated, Carrying Amount, Assets	187		174
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	4,158		3,862
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	4,158		3,862
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0
Variable Interest Entity, Consolidated, Carrying Amount, Assets	1,127		927
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	0		0
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	0		0
Other
Variable Interest Entity [Line Items]
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	0		0
Variable Interest Entity, Consolidated, Carrying Amount, Assets	0		0
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets	318		187
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	318		187
GreenPoint Manufactured Housing
Variable Interest Entity [Line Items]
Qualitative and Quantitative Information, Transferor's Continuing Involvement, Arrangements of Financial Support, Amount	12		12
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	8		8
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	410
Variable Interest Entity, Not Primary Beneficiary | Option- ARM
Variable Interest Entity [Line Items]
Continuing Involvement with Derecognized Transferred Financial Assets, Liabilities Incurred	1,361		1,499
Continuing Involvement with Derecognized Transferred Financial Assets, Amount Outstanding	1,407		1,549
Variable Interest Entity, Not Primary Beneficiary | GreenPoint HELOCs
Variable Interest Entity [Line Items]
Continuing Involvement with Derecognized Transferred Financial Assets, Liabilities Incurred	47		56
Continuing Involvement with Derecognized Transferred Financial Assets, Amount Outstanding	41		50
Variable Interest Entity, Not Primary Beneficiary | GreenPoint Manufactured Housing
Variable Interest Entity [Line Items]
Continuing Involvement with Derecognized Transferred Financial Assets, Liabilities Incurred	641		697
Continuing Involvement with Derecognized Transferred Financial Assets, Amount Outstanding	646		702
Letters of credit funded	84		$ 85
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 410