Retirement Plans and Postretirement Medical Benefits (Other Changes in Plan Assets and Benefit Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
United States
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 22,728	$ (8,003)
Prior service credit	0	(428)
Amortization of net actuarial loss	(27,220)	(29,272)
Amortization of prior service credit (cost)	60	60
Net transition asset	0	0
Settlement / curtailment	(2,109)	(1,243)
Total recognized in other comprehensive income	(6,541)	(38,886)
Foreign
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	91,549	8,663
Prior service credit	0	0
Amortization of net actuarial loss	(5,264)	(5,926)
Amortization of prior service credit (cost)	73	66
Net transition asset	8	9
Settlement / curtailment	(110)	0
Total recognized in other comprehensive income	86,256	2,812
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(13,934)	(31,253)
Amortization of net actuarial loss	(3,615)	(7,528)
Amortization of prior service credit (cost)	(297)	(297)
Total recognized in other comprehensive income	$ (17,846)	$ (39,078)