Other Long-Term Liabilities - Summary of Other Long-Term Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Asset retirement obligations	$ 7,043	$ 6,805
Dividends payable - 2015 LTIP	64	0
Escheat liability	145	220
Capital lease payable	2	6
Lease incentive	560	426
Deferred rent	371	404
Royalty payable	270	270
Total other long-term liabilities	$ 8,455	$ 8,131