Pension and Other Postretirement Benefits (Details 4) - Pension Plan [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	$ 81,503	$ 450,627
Accumulated benefit obligation	80,967	437,999
Fair value of plan assets	31,002	370,616
Total accumulated benefit obligation	485,777	481,241
Domestic Plan [Member]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	40,572	389,613
Accumulated benefit obligation	40,090	378,431
Fair value of plan assets	4,797	331,260
Foreign Plan [Member]
Defined Benefit Plan, Pension Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Projected benefit obligation	40,931	61,014
Accumulated benefit obligation	40,877	59,568
Fair value of plan assets	$ 26,205	$ 39,356