EMPLOYEE BENEFIT PLANS (Details) (USD $)	1 Months Ended	3 Months Ended
	Apr. 30, 2013	Mar. 31, 2013	Mar. 31, 2012
EMPLOYEE BENEFIT PLANS
Service cost - benefits earned during the period		$ 2,708,000	$ 2,561,000
Interest cost on projected benefit obligation		2,553,000	2,604,000
Expected return on plan assets		(2,759,000)	(2,673,000)
Amortization of prior service cost/(credit)		(95,000)	(95,000)
Amortization of actuarial losses		2,729,000	2,175,000
Total benefit cost		5,136,000	4,572,000
Contribution made by the company to its defined benefit pension plan for the plan year 2013	$ 2,300,000
Adjusted funding target percentage to be maintained		80.00%
Funded status for Pension Benefit Guaranty Corporation reporting purposes to be maintained (as a percent)		80.00%
Age of eligibility for prescription drug benefit		65 years