Components of Accumulated Other Comprehensive Income (Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, beginning of period		$ 2,009,893	$ 2,153,272	$ 2,037,670	$ 2,171,098
Reclassifications from AOCI to earnings:
Balance, end of period		1,921,927	2,112,599	1,921,927	2,112,599
Pension and Other Postretirement Employee Benefits [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, beginning of period		(28,799)	(19,154)	(28,651)	(18,925)
Reclassifications from AOCI to earnings:
Other	[1]	(197)	(305)	(394)	(611)
Tax effect		50	75	99	152
Net of tax amount		(147)	(230)	(295)	(459)
Balance, end of period		(28,946)	(19,384)	(28,946)	(19,384)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, beginning of period		126,183	137,882	142,792	121,957
Unrecognized gains (losses) arising in AOCI during the period:
Gross		(3,186)	9,325	(15,374)	31,197
Tax effect		26	(141)	110	(493)
Reclassifications from AOCI to earnings:
Gross	[2]	(4,630)	(5,697)	(9,217)	(11,416)
Tax effect		84	124	166	248
Net of tax amount		(7,706)	3,611	(24,315)	19,536
Balance, end of period		118,477	141,493	118,477	141,493
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balance, beginning of period		97,384	118,728	114,141	103,032
Reclassifications from AOCI to earnings:
Balance, end of period		$ 89,531	$ 122,109	$ 89,531	$ 122,109

[1] Included in the computation of net periodic pension costs.

[2] Included in Interest expense, net on the Condensed Consolidated Statement of Operations.