PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost		$ 848,000	$ 696,000	$ 1,746,000	$ 1,481,000
Interest cost		1,893,000	1,775,000	3,706,000	3,601,000
Expected return on plan assets		(1,897,000)	(1,726,000)	(3,983,000)	(3,541,000)
Amortizations [Abstract]
Prior service cost (credits)		49,000	48,000	97,000	100,000
Actuarial loss		1,612,000	1,048,000	2,938,000	2,057,000
Net periodic benefit cost prior to capitalized benefit costs		2,505,000	1,841,000	4,504,000	3,698,000
Capitalized benefit costs		(1,228,000)	(902,000)	(2,207,000)	(1,812,000)
Total net periodic benefit expense		1,277,000	939,000	2,297,000	1,886,000
Contributions	19,800,000
Other Postretirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost		173,000	164,000	396,000	379,000
Interest cost		563,000	597,000	1,146,000	1,216,000
Expected return on plan assets		(380,000)	(408,000)	(804,000)	(854,000)
Amortizations [Abstract]
Prior service cost (credits)		(54,000)	(64,000)	(109,000)	(135,000)
Actuarial loss		370,000	316,000	659,000	628,000
Net periodic benefit cost prior to capitalized benefit costs		672,000	605,000	1,288,000	1,234,000
Capitalized benefit costs		(329,000)	(297,000)	(631,000)	(605,000)
Total net periodic benefit expense		343,000	308,000	657,000	629,000
Defined benefit plan regulatory obligation to contribute to the plan during the period		3,600,000		3,600,000
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Amortizations [Abstract]
Estimated future contributions		$ 1,200,000		$ 1,200,000