BENEFIT PLANS (Combined Funded Status of Plans and their Reconciliation with Related Amounts Recognized in Consolidated Financial Statements) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Change in Benefit Obligation
Projected benefit obligation at beginning of year	$ 911,700,000	$ 991,338,000
Service cost	4,157,000	21,904,000
Interest cost	44,392,000	40,995,000
Plan amendments	0	(39,443,000)
Actuarial (gain) loss	167,041,000	(61,548,000)
Benefits paid	(44,068,000)	(41,546,000)
Projected benefit obligation at end of year	1,083,222,000	911,700,000	991,338,000
Change in Plan Assets
Fair value of assets at beginning of year	756,624,000	683,091,000
Actual return on plan assets	98,928,000	110,224,000
Employer contribution	5,488,000	4,855,000	4,509,000
Benefits paid	(44,068,000)	(41,546,000)
Fair value of assets at end of year	816,972,000	756,624,000	683,091,000
Funded status	(266,250,000)	(155,076,000)
Amounts Recognized in the Consolidated Balance Sheets
Noncurrent assets	0	3,056,000
Current liabilities	(13,719,000)	(11,398,000)
Noncurrent liabilities	(252,531,000)	(146,734,000)
Net amount recognized	(266,250,000)	(155,076,000)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss	249,867,000	142,173,000
Prior service cost	(356,000)	(168,000)
Total amount recognized	249,511,000	142,005,000
Other Postretirement Benefit Plans, Defined Benefit
Change in Benefit Obligation
Projected benefit obligation at beginning of year	92,888,000	113,500,000
Service cost	2,146,000	2,830,000	4,409,000
Interest cost	3,297,000	3,260,000	5,851,000
Liability reduction from curtailment	(2,639,000)	0
Actuarial (gain) loss	(2,617,000)	(20,444,000)
Benefits paid	(7,739,000)	(6,258,000)	(6,834,000)
Projected benefit obligation at end of year	85,336,000	92,888,000	113,500,000
Change in Plan Assets
Fair value of assets at beginning of year	0	0
Actual return on plan assets	0	0
Benefits paid	(7,739,000)	(6,258,000)	(6,834,000)
Fair value of assets at end of year	0	0	0
Funded status	(85,336,000)	(92,888,000)
Amounts Recognized in the Consolidated Balance Sheets
Current liabilities	(8,964,000)	(9,431,000)
Noncurrent liabilities	(76,372,000)	(83,457,000)
Net amount recognized	(85,336,000)	(92,888,000)
Amounts Recognized in Accumulated Other Comprehensive Income
Net actuarial loss	10,921,000	16,405,000
Prior service cost	(28,160,000)	(36,319,000)
Total amount recognized	$ (17,239,000)	$ (19,914,000)