Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Unrealized gains (losses)	$ 18,245	$ (3,092)
Amounts reclassified from accumulated other comprehensive income (loss)	4,684	(995)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	20,367	24,454
Ending balance	43,296	20,367
Derivative Instruments
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	647	0
Unrealized gains (losses)	(4,359)	497
Amounts reclassified from accumulated other comprehensive income (loss)	7,040	150
Ending balance	3,328	647
Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	19,720	24,067
Unrealized gains (losses)	22,923	(3,589)
Amounts reclassified from accumulated other comprehensive income (loss)	(2,332)	(758)
Ending balance	40,311	19,720
Available-for-Sale Securities
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Beginning balance	0	387
Unrealized gains (losses)	(319)	0
Amounts reclassified from accumulated other comprehensive income (loss)	(24)	(387)
Ending balance	$ (343)	$ 0