Private Education Loans - Schedule of Estimated Fair Value, Accretable Yield and Expected Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013	Sep. 30, 2014
PEAKS Trust Student Loans [Member]
Acquired Impaired Loans Rollforward [Line Items]
Estimated fair value	$ 112,116
Accretable yield	100,953
Expected cash flows	213,069
PEAKS Trust Student Loans [Member] | Analogy [Member]
Acquired Impaired Loans Rollforward [Line Items]
Estimated fair value	60,177
Accretable yield	58,843
Expected cash flows	119,020
CUSO Student Loans [Member]
Acquired Impaired Loans Rollforward [Line Items]
Estimated fair value		27,199
Accretable yield		12,498
Expected cash flows		39,697
CUSO Student Loans [Member] | Analogy [Member]
Acquired Impaired Loans Rollforward [Line Items]
Estimated fair value		12,799
Accretable yield		5,651
Expected cash flows		$ 18,450