EMPLOYEE BENEFIT PLANS (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2011	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
EMPLOYEE BENEFIT PLANS
Service cost - benefits earned during the period		$ 2,194,000	$ 2,068,000	$ 4,388,000	$ 4,136,000
Interest cost on projected benefit obligation		2,508,000	2,357,000	5,016,000	4,714,000
Expected return on plan assets		(2,512,000)	(2,312,000)	(5,024,000)	(4,624,000)
Amortization of prior service cost		(98,000)	(98,000)	(196,000)	(196,000)
Amortization of actuarial losses		1,388,000	1,026,000	2,776,000	2,052,000
Total benefit cost		3,480,000	3,041,000	6,960,000	6,082,000
Contribution made by the Company to its defined benefit pension plan for the 2010 plan year				2,100,000
Contribution made by the Company to its defined benefit pension plan for the 2011 plan year	$ 2,300,000			$ 2,300,000
Adjusted funding target percentage, minimum (as a percent)				80.00%
Age of closed group of retirees to whom the entity provides a prescription drug benefit, minimum				65