Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
Products	$ 74,522	$ 82,302	$ 140,682	$ 164,707
Rentals	8,747	15,065	20,571	28,989
Services	3,761	7,951	8,151	14,197
Total revenue	87,030	105,318	169,404	207,893
Cost of revenue:
Products	50,189	49,995	95,850	97,731
Rentals	3,687	7,654	9,943	14,165
Services	2,089	3,265	4,124	5,978
Depreciation	1,813	2,094	3,708	4,029
Total cost of revenue	$ 57,778	$ 63,008	$ 113,625	$ 121,903