Income Taxes - Significant Components of Net Deferred Income Taxes (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax liability:
Depreciation	$ (15,423)	$ (15,620)
Unrealized gain on securities held for sale	0	0
Prepaid expenses	(169)	(123)
Net deferred tax liability	(593)	(267)
Allowance for doubtful accounts	55	20
Inventory reserves	918	1,340
Accrued liabilities	57	76
Warrant interest expense	269	277
Stock compensation expense	2,689	2,850
State net operating loss-net of tax	5,923	3,500
Net operating loss carryforward	31,658	16,206
Unrealized loss on securities held for sale		240
Tax credits	581	514
Valuation allowance	(27,151)	(9,547)
Total deferred tax assets	$ 14,999	$ 15,476