Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenue:
Products	$ 67,155	$ 74,522	$ 133,030	$ 140,682
Rentals	3,146	8,747	7,198	20,571
Services	2,018	3,761	4,380	8,151
Total revenue	72,319	87,030	144,608	169,404
Cost of revenue:
Products	44,919	50,189	87,391	95,850
Rentals	1,026	3,687	2,326	9,943
Services	1,615	2,089	3,712	4,124
Depreciation	838	1,813	2,330	3,708
Total cost of revenue	$ 48,398	$ 57,778	$ 95,759	$ 113,625