LHFI by Credit Quality Indicator (Additional Information) (Detail) - Internal Credit Assessment [Domain] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Held-for-sale, Fair Value Disclosure		$ 1,866		$ 1,866		$ 1,892
Impaired Financing Receivable, Interest Income, Cash Basis Method		1	$ 1	1	$ 2
Loans Receivable, Fair Value Disclosure		263		263		272
Loans and Leases Receivable, Gross	[1]	132,538		132,538		133,112
Residential Guaranteed [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		625		625		632
Federally Guaranteed Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross		4,401		4,401		4,827
Federal Home Loan Bank Advances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Pledged as Collateral		$ 31,200		$ 31,200		$ 31,200
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Government Guarantee Percent		2.00%		2.00%		2.00%
Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Modifications, Recorded Investment		$ 2,500		$ 2,500		$ 2,500

[1] Includes loans of consolidated VIEs of $266 million and $288 million at June 30, 2015 and December 31, 2014, respectively.