Acquisitions and Discontinued Operations - Components of Assets and Liabilities of Education Lending Business (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Unearned income on loans	$ (776)	$ (805)	$ (923)
Segment, Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Unearned income on loans	(6)	(6)	(5)
Segment, Discontinued Operations [Member] | Education Lending [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Unearned income on loans	$ (6)	$ (6)	$ (5)