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
	Mar. 31, 2018	Mar. 31, 2017
Class of Warrant or Right [Line Items]
Reduction to net sales	$ 471	$ 932
Income tax benefit	$ 118	$ 348