Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities of PEAKS Trust (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Allowance for loan losses	$ 44,392	$ 29,349
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Allowance for loan losses	$ 42,353	$ 29,349

A valuation allowance relating to a written agreement to receive money (at a specified future date(s) more than one year from the reporting date, consisting of principal as well as any accrued interest) for the portion that is expected to be uncollectible.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 4

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5074-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.4)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_AllowanceForNotesAndLoansReceivableNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant