Revenue Recognition (Analysis of Product Return Liability) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Revenue Recognition
Beginning balance	$ 3,143	$ 2,621	$ 2,621
Provision for product returns	1,062	(255)
Credits issued to third parties	(462)	(493)
Ending balance	3,743	$ 1,873	3,143
Sales not recognized in revenues due to insufficient information available to estimate a reasonable product return accrual	$ 700		$ 500
Aggregate product return rate	1.10%	1.10%