ACCUMULATED OTHER COMPREHENSIVE LOSS (Changes in Components of AOCI, Net of Related Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Balance, beginning	$ 1,029,680	$ 1,017,987	$ 1,022,293	$ 1,009,855
Other comprehensive loss, net of tax	(1,119)	(6,976)	(15,511)	(10,353)
Balance, ending	1,072,053	995,338	1,072,053	995,338
Accumulated Other Comprehensive Loss [Member]
Balance, beginning	(34,962)	(33,306)	(20,570)	(29,929)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	(2,764)	(8,709)	(18,292)	(13,907)
Amounts reclassified from accumulated other comprehensive loss	1,645	1,733	2,781	3,554
Other comprehensive loss, net of tax	(1,119)	(6,976)	(15,511)	(10,353)
Balance, ending	(36,081)	(40,282)	(36,081)	(40,282)
Unrealized losses on cash flow hedges [Member]
Balance, beginning	(26,717)	(24,698)	(11,732)	(21,520)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	(2,828)	(8,936)	(18,949)	(13,935)
Amounts reclassified from accumulated other comprehensive loss	1,645	1,733	2,781	3,554
Balance, ending	(27,900)	(31,901)	(27,900)	(31,901)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Balance, beginning	(8,245)	(8,608)	(8,838)	(8,409)
Current period change, excluding amounts reclassified from accumulated other comprehensive loss	64	227	657	28
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Balance, ending	$ (8,181)	$ (8,381)	$ (8,181)	$ (8,381)