Income Taxes - Deferred Tax Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Allowance for uncollectible accounts receivable	$ 348	$ 188
Accrued compensation expense	3,954	3,064
Inventory differences	1,949	364
Net operating loss carry-forwards	19,622	22,689
Deferred revenue	237	273
Stock-based compensation expense	2,465	2,166
Uncertain tax positions	709	1,052
Other	3,762	1,848
Total deferred income tax assets	33,046	31,644
Prepaid expenses	(757)	(823)
Property and equipment	(19,001)	(17,236)
Intangible assets	(4,107)	(6,169)
Other	(1,116)	(97)
Total deferred income tax liabilities	(24,981)	(24,325)
Valuation allowance	(1,225)	(361)
Net deferred income tax assets	6,840	6,958
Deferred income tax assets - Current	4,976	3,704
Deferred income tax assets - Long-term	4,237	5,366
Deferred income tax liabilities - Long-term	$ (2,373)	$ (2,112)