Other Noncurrent Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Pension and retiree medical obligations	$ 100,762	$ 93,604
Liability for uncertain tax positions	1,872	2,623
Deferred revenue	2,167	2,442
Other	18,076	22,561
Total other noncurrent liabilities	$ 122,877	$ 121,230