BENEFIT PLANS (Combined Funded Status of Plans and their Reconciliation with Related Amounts Recognized in Consolidated Financial Statements - Pension Benefits) (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Benefit Obligation
Projected benefit obligation at beginning of year	$ 1,090,893	$ 958,936
Service cost	4,899	4,995	$ 5,716
Interest cost	29,335	37,640	35,503
Actuarial (gain) loss	89,109	141,922
Benefits paid	(154,691)	(52,600)
Projected benefit obligation at end of year	1,059,545	1,090,893	958,936
Change in Fair Value of Plan Assets
Fair value of assets at beginning of year	949,007	836,770
Actual return on plan assets	141,155	155,955
Employer contributions	8,819	8,882	109,631
Benefits paid	(154,691)	(52,600)
Fair value of assets at end of year	944,290	949,007	$ 836,770
Funded status	(115,255)	(141,886)
Amounts Recognized in the Consolidated Balance Sheets
Noncurrent assets	0	9,056
Current liabilities	(8,060)	(8,579)
Noncurrent liabilities	(107,195)	(142,363)
Net amount recognized	(115,255)	(141,886)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss	230,452	268,483
Prior service cost	5,148	6,488
Total amount recognized	$ 235,600	$ 274,971