Employee Benefit Plans (Amounts Recognized In Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amounts recognized in consolidated balance sheet:
Long-term pension and benefit cost	$ 111,305	$ 71,461
Accumulated other comprehensive loss:
Accumulated Other Comprehensive Income (Loss), Net of Tax	(137,578)	(101,241)
Pension Plan [Member]
Amounts recognized in consolidated balance sheet:
Current accrued benefit cost	0	0
Long-term pension and benefit cost	99,170	59,064
Net amount recognized in consolidated balance sheet	99,170	59,064
Accumulated other comprehensive loss:
Net actuarial loss	(100,474)	(62,013)
Prior service credit	3,248	3,429
Accumulated Other Comprehensive Income (Loss), Net of Tax	(97,226)	(58,584)	$ (62,279)	$ (63,257)
Amount of Liabilities and Accumulated Other Comprehensive Loss Recognized in Consolidated Balance Sheet	1,944	480
Other Postretirement Benefits [Member]
Amounts recognized in consolidated balance sheet:
Current accrued benefit cost	625	614
Long-term pension and benefit cost	12,135	12,397
Net amount recognized in consolidated balance sheet	12,760	13,011
Accumulated other comprehensive loss:
Net actuarial loss	(6,597)	(7,881)
Prior service credit	0	0
Accumulated Other Comprehensive Income (Loss), Net of Tax	(6,597)	(7,881)	$ (3,945)	$ (1,696)
Amount of Liabilities and Accumulated Other Comprehensive Loss Recognized in Consolidated Balance Sheet	$ 6,163	$ 5,130