Unaudited Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Revenue	$ 87,030	$ 105,318	$ 169,404	$ 207,893
Cost of revenue	57,778	63,008	113,625	121,903
Gross margin	29,252	42,310	55,779	85,990
Expenses:
Selling, general and administrative	23,021	20,854	46,588	42,426
Depreciation and amortization	2,797	2,501	5,473	4,785
Research and development	1,670	1,280	3,242	2,306
Impairment of inventory and rental equipment	20,372	0	20,372	0
Total expenses	47,860	24,635	75,675	49,517
Income (loss) from operations	(18,608)	17,675	(19,896)	36,473
Other income (expense):
Interest expense	(420)	(381)	(828)	(836)
Other income (expense), net	(2)	(272)	(227)	(218)
Total other income (expense)	(422)	(653)	(1,055)	(1,054)
Income (loss) before income taxes	(19,030)	17,022	(20,951)	35,419
Income tax benefit (expense)	6,483	(5,981)	6,889	(12,361)
Net income (loss)	$ (12,547)	$ 11,041	$ (14,062)	$ 23,058
Earnings (loss) per common share:
Basic earnings (loss) per common share (in dollars per share)	$ (0.23)	$ 0.20	$ (0.26)	$ 0.42
Diluted earnings (loss) per common share (in dollars per share)	$ (0.23)	$ 0.20	$ (0.26)	$ 0.42
Weighted average common shares:
Weighted average common shares used in computing basic earnings (loss) per common share	54,264	54,645	54,356	54,299
Weighted average common shares used in computing diluted earnings (loss) per common share	54,264	55,533	54,356	55,473