Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	$ 704,821
Unrealized gains	3,970
Amounts reclassified from AOCI	(876)
Ending Balance	699,947
Accumulated Other Comprehensive Income
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	43,296
Ending Balance	46,390
Derivative instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	3,328
Unrealized gains	3,593
Amounts reclassified from AOCI	(876)
Ending Balance	6,045
Pension, postretirement and other post-employment benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	40,311
Unrealized gains	0
Amounts reclassified from AOCI	0
Ending Balance	40,311
Available-for-sale securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning Balance	(343)
Unrealized gains	377
Amounts reclassified from AOCI	0
Ending Balance	$ 34