Private Education Loans - Schedule of Contractually Required Future Principal and Interest Payments, Expected Cash Flows and Nonaccretable Difference (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013	Sep. 30, 2014
PEAKS Trust Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual future principal and interest payments	$ 487,800
Expected cash flows	213,069
Nonaccretable difference	274,731
PEAKS Trust Student Loans [Member] | Analogy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual future principal and interest payments	213,600
Expected cash flows	119,020
Nonaccretable difference	94,580
CUSO Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual future principal and interest payments		111,159
Expected cash flows		39,697
Nonaccretable difference		71,462
CUSO Student Loans [Member] | Analogy [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractual future principal and interest payments		36,715
Expected cash flows		18,450
Nonaccretable difference		$ 18,265