PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $)	1 Months Ended		3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost			$ 1,033,000	$ 848,000	$ 2,080,000	$ 1,746,000
Interest cost			1,851,000	1,893,000	3,623,000	3,706,000
Expected return on plan assets			(2,302,000)	(1,897,000)	(4,573,000)	(3,983,000)
Amortizations [Abstract]
Prior service cost (credits)			48,000	49,000	96,000	97,000
Actuarial loss			1,807,000	1,612,000	3,456,000	2,938,000
Net periodic benefit cost prior to capitalized benefit costs			2,437,000	2,505,000	4,682,000	4,504,000
Capitalized benefit costs			(1,268,000)	(1,228,000)	(2,435,000)	(2,207,000)
Total net periodic benefit expense			1,169,000	1,277,000	2,247,000	2,297,000
Contributions	9,100,000	19,800,000
Other Postretirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost			187,000	173,000	425,000	396,000
Interest cost			482,000	563,000	1,017,000	1,146,000
Expected return on plan assets			(437,000)	(380,000)	(886,000)	(804,000)
Amortizations [Abstract]
Prior service cost (credits)			(52,000)	(54,000)	(106,000)	(109,000)
Actuarial loss			297,000	370,000	648,000	659,000
Net periodic benefit cost prior to capitalized benefit costs			477,000	672,000	1,098,000	1,288,000
Capitalized benefit costs			(249,000)	(329,000)	(571,000)	(631,000)
Total net periodic benefit expense			228,000	343,000	527,000	657,000
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