Performance-Based Common Stock Warrants - Impact to Net Sales in Connection with Warrants and Related Income Tax Benefit (Details) - Common Stock Purchase Warrants - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Warrant or Right [Line Items]
Reduction/(increase) to net sales	$ (128)	$ 331	$ 343	$ 1,263
Income tax benefit/(expense)	$ (32)	$ 123	$ 86	$ 471