Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 640,536
Unrealized gains	(14,421)
Amounts reclassified from AOCI	(37)
Ending Balance	365,646
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	5,689
Ending Balance	(8,769)
Derivative instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(2,564)
Unrealized gains	(3,039)
Amounts reclassified from AOCI	1,209
Ending Balance	(4,394)
Pension, postretirement and other post-employment benefits
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	8,273
Unrealized gains	(11,461)
Amounts reclassified from AOCI	(979)
Ending Balance	(4,166)
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(20)
Unrealized gains	79
Amounts reclassified from AOCI	(268)
Ending Balance	$ (209)