Pension (Accumulated Benefit Obligation in Excess of Plan Assets) (Details) - Pension Plan - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 300,854	$ 364,809
Accumulated benefit obligation	295,942	359,842
Fair value of plan assets	255,115	318,414
U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	268,887	336,648
Accumulated benefit obligation	268,887	336,648
Fair value of plan assets	255,115	318,414
Non-U.S. Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	31,967	28,161
Accumulated benefit obligation	27,055	23,194
Fair value of plan assets	$ 0	$ 0