Components of Accumulated Other Comprehensive Income (Loss) (Changes in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	$ (1,843,551)	$ (1,611,789)	$ (1,526,133)	$ (1,304,953)
Effect of pension settlement	0	0	(10,553)	0
Balance at end of period	(2,405,419)	(1,660,106)	(2,405,419)	(1,660,106)
Pension Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	41,274	73,592	49,579	79,025
Net (gain) loss arising during the period	0	0	4,587	0
Effect of pension settlement	0	0	(10,553)	0
Amounts reclassified from AOCI to earnings	(869)	(2,664)	(3,208)	(8,097)
Balance at end of period	40,405	70,928	40,405	70,928
Other Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	1,700	14,418	1,790	14,783
Amounts reclassified from AOCI to earnings	(45)	(182)	(135)	(547)
Balance at end of period	1,655	14,236	1,655	14,236
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(93,936)	(5,763)	(8,131)	27,181
Net (gain) loss arising during the period	(32,895)	(4,310)	(115,256)	(32,741)
Amounts reclassified from AOCI to earnings	170	(2,326)	(3,274)	(6,839)
Balance at end of period	(126,661)	(12,399)	(126,661)	(12,399)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance at beginning of period	(50,962)	82,247	43,238	120,989
Balance at end of period	$ (84,601)	$ 72,765	$ (84,601)	$ 72,765