Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Revenue	$ 334,359	$ 449,157	$ 371,065
Cost of revenue	219,249	266,198	223,538
Gross margin	115,110	182,959	147,527
Expenses:
Selling, general and administrative	95,483	87,146	78,197
Depreciation and amortization	11,006	9,738	7,273
Research and development	7,455	4,976	3,752
Impairment of inventory and rental equipment	20,372	0	0
(Gain) loss on disposal of long-lived assets	(33)	211	(421)
Total expenses	134,283	102,071	88,801
Income (loss) from operations	(19,173)	80,888	58,726
Other income (expense):
Interest expense	(1,762)	(1,610)	(2,092)
Other income (expense), net	(181)	(394)	316
Total other income (expense)	(1,943)	(2,004)	(1,776)
Income (loss) before income taxes	(21,116)	78,884	56,950
Income tax benefit (expense)	7,654	(25,281)	(20,772)
Net income (loss)	$ (13,462)	$ 53,603	$ 36,178
Earnings (loss) per common share:
Basic earnings (loss) per common share (in dollars per share)	$ (0.25)	$ 0.98	$ 0.70
Diluted earnings (loss) per common share (in dollars per share)	$ (0.25)	$ 0.97	$ 0.67
Weighted average common shares:
Weighted average common shares used in computing basic earnings (loss) per common share (in shares)	54,459	54,511	51,346
Weighted average common shares used in computing diluted earnings (loss) per common share (in shares)	54,459	55,526	53,841