PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 point	Dec. 31, 2010	Dec. 31, 2009
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	1,063,000
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	196,820,000	178,857,000
Service cost	10,634,000	10,401,000	10,053,000
Interest cost	11,211,000	10,811,000	9,981,000
Participant contributions	137,000	280,000
Actuarial loss (gain)	23,180,000	130,000
Benefits paid	(4,179,000)	(3,272,000)
Liability gain due to Curtailment	(5,361,000)	(387,000)
Projected benefit obligation at the end of the period	232,442,000	196,820,000	178,857,000
Accumulated benefit obligation at the end of the period	226,051,000	184,933,000
Change in plan assets:
Fair value of plan assets at the beginning of the period	152,015,000	128,331,000
Actual return on plan assets	1,277,000	16,676,000
Employer contributions	9,981,000	10,000,000
Participant contributions	137,000	280,000
Benefits paid	(4,179,000)	(3,272,000)
Fair value of plan assets at the end of the period	159,231,000	152,015,000	128,331,000
Funded status	(73,211,000)	(44,805,000)
Weighted-average assumptions used in computing the benefit obligation
Discount rate (as a percent)	5.15%	5.75%
Expected return on plan assets (as a percent)	7.10%	8.20%
Rate of compensation increase (as a percent)	2.50%	2.50%
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	26,783,000	25,087,000
Service cost	476,000	452,000	429,000
Interest cost	1,114,000	1,481,000	1,477,000
Participant contributions	(12,218,000)	565,000
Actuarial loss (gain)	(2,939,000)	1,450,000
Benefits paid	699,000	(1,879,000)
Liability gain due to Curtailment	(2,030,000)	(373,000)
Projected benefit obligation at the end of the period	11,885,000	26,783,000	25,087,000
Change in plan assets:
Employer contributions	1,331,000	1,314,000
Participant contributions	699,000	565,000
Benefits paid	(2,030,000)	(1,879,000)
Funded status	$ (11,885,000)	$ (26,783,000)
Other Benefits | Maximum
Weighted-average assumptions used in computing the benefit obligation
Discount rate (as a percent)	5.05%	5.85%
Other Benefits | Minimum
Weighted-average assumptions used in computing the benefit obligation
Discount rate (as a percent)	3.40%	4.65%