Notes Payable - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2018	Mar. 19, 2012
13% Senior First Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount		$ 110.0
Notes maturity date	Mar. 19, 2030
13% Senior Second Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount		$ 20.0
Notes maturity date	Mar. 19, 2030

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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