Notes Payable - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 19, 2012
Debt Instrument [Line Items]
Collateral Account used for future payments		$ 400
Total outstanding amounts of notes		18,774
Principal payments	$ 18,774	2,969	$ 10,395
Cash interest paid on Notes	$ 1,991	2,647	2,887
13% Senior First Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount				$ 110,000
Notes maturity date	Mar. 19, 2030
13% Senior Second Lien Notes [Member]
Debt Instrument [Line Items]
Issued aggregate principal amount				$ 20,000
Notes maturity date	Mar. 19, 2030
Total outstanding amounts of notes	$ 0	18,800
13% Senior First And Second Lien Notes [Member]
Debt Instrument [Line Items]
Principal payments	18,800	2,900
Cash interest paid on Notes	$ 2,000	$ 2,600	$ 2,900