Equity Method Investments - Operating Results (Details) - ICP - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
ICP’s Operating results:
Net sales	$ 0	$ 44,019	$ 78,062	$ 134,204
Cost of sales and expenses	0	41,805	79,224	126,671
Net income	$ 0	$ 2,214	$ (1,162)	$ 7,533