PENSION AND POST RETIREMENT BENEFIT PLANS (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2012
Components of net periodic pension benefit Gain
Interest and service cost	$ 2,337,000	$ 2,520,000
Expected return on plan assets	(2,961,000)	(3,016,000)
Amortization of net loss	632,000	450,000
Net periodic benefit gain	8,000	(46,000)
Contribution by employer	2,100,000	4,100,000	4,900,000
Further contributions to defined benefit retirement plan during the fiscal year				$ 2,900,000