Commitments - Long-term Supply Contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Future minimum purchase requirements
2017	$ 21,375
2018	23,299
2019	1,491
2020	846
2021	781
Total payments	22,562	$ 29,703	$ 40,259
Raw and other materials
Future minimum purchase requirements
2017	19,190
2018	21,049
2019	781
2020	781
2021	781
Total payments	21,178	27,832	38,096
Information systems and services
Future minimum purchase requirements
2017	2,185
2018	2,250
2019	710
2020	65
Total payments	$ 1,384	$ 1,871	$ 2,163