BENEFIT PLANS (Combined Funded Status of Plans and their Reconciliation with Related Amounts Recognized in Consolidated Financial Statements) (Details) - Pension Benefits [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in Benefit Obligation
Projected benefit obligation at beginning of year	$ 988,453	$ 1,083,222
Service cost	5,343	4,851	$ 4,157
Interest cost	36,505	44,065	44,392
Actuarial (gain) loss	24,675	(63,725)
Benefits paid	(48,302)	(79,960)
Projected benefit obligation at end of year	1,006,674	988,453	1,083,222
Change in Fair Value of Plan Assets
Fair value of assets at beginning of year	745,686	816,972
Actual return on plan assets	42,555	(5,373)
Employer contributions	9,576	14,047	5,488
Benefits paid	(48,302)	(79,960)
Fair value of assets at end of year	749,515	745,686	$ 816,972
Funded status	(257,159)	(242,767)
Amounts Recognized in the Consolidated Balance Sheets
Noncurrent assets	0	0
Current liabilities	(9,375)	(9,106)
Noncurrent liabilities	(247,784)	(233,661)
Net amount recognized	(257,159)	(242,767)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial (gain) loss	250,099	222,580
Prior service credit	(361)	(404)
Total amount recognized	$ 249,738	$ 222,176