PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
PENSION AND OTHER POSTRETIREMENT BENEFITS
Requisite points for participation	70
Gain on modification to pension plans and other postretirement plan		$ 5,400,000
Change in projected benefit obligation:
Liability gain due to Curtailment		5,445,000	338,000
Pension Benefits
PENSION AND OTHER POSTRETIREMENT BENEFITS
Number of plans	2
Number of plans covering nonunion employees	1
Change in projected benefit obligation:
Projected benefit obligation at the beginning of the period	232,442,000	196,820,000
Service cost	7,209,000	10,634,000	10,401,000
Interest cost	11,819,000	11,211,000	10,811,000
Participant contributions	15,000	137,000
Actuarial loss (gain)	31,551,000	23,180,000
Benefits paid	(4,620,000)	(4,179,000)
Liability gain due to Curtailment		(5,361,000)
Projected benefit obligation at the end of the period	278,416,000	232,442,000	196,820,000
Accumulated benefit obligation at the end of the period	271,116,000	226,051,000
Change in plan assets:
Fair value of plan assets at the beginning of the period	159,231,000	152,015,000
Actual return on plan assets	21,888,000	1,277,000
Employer contributions	16,875,000	9,981,000
Participant contributions	15,000	137,000
Benefits paid	(4,620,000)	(4,179,000)
Fair value of plan assets at the end of the period	193,389,000	159,231,000	152,015,000
Funded status	(85,027,000)	(73,211,000)
Assumptions used in computing the benefit obligation
Expected return on plan assets (as a percent)	7.10%	7.10%
Rate of compensation increase (as a percent)	2.50%	2.50%
Pension Benefits | Maximum
Assumptions used in computing the benefit obligation
Discount rate (as a percent)	4.40%	5.15%
Pension Benefits | Minimum
Assumptions used in computing the benefit obligation
Discount rate (as a percent)	4.30%	5.10%
Other Benefits
PENSION AND OTHER POSTRETIREMENT BENEFITS
Number of plans	2
Number of plans covering nonunion employees	1
Change in projected benefit obligation:
Projected benefit obligation at the beginning of the period	11,885,000	26,783,000
Service cost	50,000	476,000	452,000
Interest cost	457,000	1,114,000	1,481,000
Plan Amendments		(12,218,000)
Participant contributions		699,000
Actuarial loss (gain)	(292,000)	(2,939,000)
Benefits paid	433,000	(2,030,000)
Liability gain due to Curtailment	(1,387,000)
Projected benefit obligation at the end of the period	11,146,000	11,885,000	26,783,000
Change in plan assets:
Employer contributions	954,000	1,331,000
Participant contributions	433,000	699,000
Benefits paid	(1,387,000)	(2,030,000)
Funded status	(11,146,000)	$ (11,885,000)
Other Benefits | Maximum
Assumptions used in computing the benefit obligation
Discount rate (as a percent)	4.25%	5.05%
Other Benefits | Minimum
Assumptions used in computing the benefit obligation
Discount rate (as a percent)	2.25%	3.40%