Pension and Other Postretirement Benefits (Details 5) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Accrued liabilities	$ 8,294	$ 8,261
Accrued retirement benefits	89,000	109,350
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	15,287	3,017
Accrued liabilities	3,230	3,180
Accrued retirement benefits	55,729	76,877
Accumulated other non-owner changes to equity, net	(98,006)	(110,988)
Net actuarial loss	(95,973)	(109,594)
Prior service costs	(2,033)	(1,394)
Pension Plan [Member] | Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	4,242	0
Accrued liabilities	2,823	2,813
Accrued retirement benefits	41,410	55,540
Accumulated other non-owner changes to equity, net	(84,990)	(91,530)
Net actuarial loss	(82,736)	(89,772)
Prior service costs	(2,254)	(1,758)
Pension Plan [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other assets	11,045	3,017
Accrued liabilities	407	367
Accrued retirement benefits	14,319	21,337
Accumulated other non-owner changes to equity, net	(13,016)	(19,458)
Net actuarial loss	(13,237)	(19,822)
Prior service costs	221	364
Other postretirement benefit plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued liabilities	5,064	5,081
Accrued retirement benefits	32,506	31,772
Accumulated other non-owner changes to equity, net	(5,838)	(3,582)
Net actuarial loss	(5,746)	(3,532)
Prior service costs	$ (92)	$ (50)