Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Products									$ 283,493	$ 354,356	$ 282,639
Rentals									35,242	65,549	62,042
Services									15,624	29,252	26,384
Total revenues	$ 77,014	$ 87,942	$ 87,030	$ 82,373	$ 124,503	$ 116,761	$ 105,318	$ 102,575	334,359	449,157	371,065
Cost of Revenue:
Products									187,511	214,417	180,800
Rentals									16,052	31,285	24,987
Services									8,668	12,385	9,916
Depreciation									7,018	8,111	7,835
Total cost of revenue									$ 219,249	$ 266,198	$ 223,538