Acquisitions and Discontinued Operations - Change in Fair Values of Level 3 Consolidated Education Loan Securitization Trusts and Portfolio Loans (Parenthetical) (Detail) (Segment, Discontinued Operations [Member], Education Lending [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Segment, Discontinued Operations [Member] | Education Lending [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Issuances transfers	$ 0	$ 0