Equity Method Investments - Operating Results (Details) - ICP - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
ICP’s Operating results:
Net sales	$ 39,677	$ 40,576	$ 78,062	$ 90,185
Cost of sales and expenses	42,410	36,980	79,224	84,866
Net income	$ (2,733)	$ 3,596	$ (1,162)	$ 5,319