EMPLOYEE BENEFIT PLANS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Amounts recognized in the consolidated balance sheets
Noncurrent liabilities (included in pension and postretirement liabilities)	$ (26,847)	$ (104,673)
Components of net periodic benefit cost
Pension settlement expense	2,111	0	1,125
Nonunion Defined Benefit Pension Plan
Change in benefit obligation
Benefit obligations at beginning of year	260,950	244,402
Service cost	4,734	9,189	8,655
Interest cost	7,784	8,692	9,954
Actuarial (gain) loss	(10,797)	15,893
Benefits paid	(22,486)	(17,226)
Curtailment gain	(29,262)	0
Settlement loss	737	0
Benefit obligations at end of year	211,660	260,950	244,402
Changes in plan assets
Fair value of plan assets at beginning of year	181,225	161,249
Actual return on plan assets	31,074	19,202
Employer contributions	17,800	18,000
Benefits paid	(22,486)	(17,226)
Fair value of plan assets at end of year	207,613	181,225	161,249
Funded status	(4,047)	(79,725)
Accumulated benefit obligation	211,660	230,305
Amounts recognized in the consolidated balance sheets
Noncurrent liabilities (included in pension and postretirement liabilities)	(4,047)	(79,725)
Liabilities recognized	(4,047)	(79,725)
Components of net periodic benefit cost
Service cost	4,734	9,189	8,655
Interest cost	7,784	8,692	9,954
Expected return on plan assets	(13,313)	(12,063)	(12,584)
Pension settlement expense	2,111	0	0
Amortization of net actuarial loss	7,140	10,767	6,921
Net periodic benefit cost	8,456	16,585	12,946
Supplemental Benefit Plan
Change in benefit obligation
Benefit obligations at beginning of year	7,213	7,620
Interest cost	150	210	386
Actuarial (gain) loss	(271)	509
Benefits paid	0	(1,126)	(2,526)
Benefit obligations at end of year	7,092	7,213	7,620
Changes in plan assets
Employer contributions	0	1,126
Benefits paid	0	(1,126)	(2,526)
Funded status	(7,092)	(7,213)
Accumulated benefit obligation	7,092	7,213
Amounts recognized in the consolidated balance sheets
Noncurrent liabilities (included in pension and postretirement liabilities)	(7,092)	(7,213)
Liabilities recognized	(7,092)	(7,213)
Components of net periodic benefit cost
Interest cost	150	210	386
Pension settlement expense	0	0	1,125
Amortization of net actuarial loss	260	202	328
Net periodic benefit cost	410	412	1,839
Postretirement Health Benefit Plan
Employee Benefit Plans
Unrecognized prior service credit, amortization period	8 years
Change in benefit obligation
Benefit obligations at beginning of year	18,308	17,553
Service cost	331	315	224
Interest cost	751	749	781
Actuarial (gain) loss	(2,484)	277
Benefits paid	(588)	(586)
Benefit obligations at end of year	16,318	18,308	17,553
Changes in plan assets
Employer contributions	588	586
Benefits paid	(588)	(586)
Funded status	(16,318)	(18,308)
Accumulated benefit obligation	16,318	18,308
Amounts recognized in the consolidated balance sheets
Current liabilities (included in accrued expenses)	(610)	(573)
Noncurrent liabilities (included in pension and postretirement liabilities)	(15,708)	(17,735)
Liabilities recognized	(16,318)	(18,308)
Components of net periodic benefit cost
Service cost	331	315	224
Interest cost	751	749	781
Amortization of prior service credit	(190)	(190)	(190)
Amortization of net actuarial loss	535	416	112
Net periodic benefit cost	$ 1,427	$ 1,290	$ 927