PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $)	1 Months Ended		3 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Mar. 31, 2013	Mar. 31, 2012
Pension Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost			$ 1,047,000	$ 898,000
Interest cost			1,772,000	1,813,000
Expected return on plan assets			(2,271,000)	(2,085,000)
Amortizations [Abstract]
Prior service cost (credits)			48,000	47,000
Actuarial loss			1,649,000	1,326,000
Net periodic benefit cost prior to capitalized benefit costs			2,245,000	1,999,000
Capitalized benefit costs			(1,167,000)	(980,000)
Total net periodic benefit expense			1,078,000	1,019,000
Contributions	9,100,000	19,800,000
Other Postretirement Benefits [Member]
Net periodic benefit cost [Abstract]
Service cost			238,000	223,000
Interest cost			535,000	583,000
Expected return on plan assets			(449,000)	(424,000)
Amortizations [Abstract]
Prior service cost (credits)			(54,000)	(54,000)
Actuarial loss			351,000	289,000
Net periodic benefit cost prior to capitalized benefit costs			621,000	617,000
Capitalized benefit costs			(322,000)	(302,000)
Total net periodic benefit expense			299,000	315,000
Defined benefit plan regulatory obligation to contribute to the plan during the period			3,600,000
Supplemental Employee Retirement Plans, Defined Benefit [Member]
Amortizations [Abstract]
Estimated future contributions			$ 1,200,000