Other Noncurrent Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other Liabilities Disclosure [Abstract]
Pension and retiree medical obligations	$ 100,356	$ 93,604
Liability for uncertain tax positions	1,507	2,623
Deferred revenue	2,205	2,442
Other	18,869	22,561
Total other noncurrent liabilities	$ 122,937	$ 121,230