Performance-Based Common Stock Warrants - Impact to Net Sales Due to Warrants (Details) - Performance-based warrants - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Reduction to net sales	$ 683	$ 2,728
Income tax benefit	$ 255	$ 1,000