PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 1,802	$ 2,628
Interest cost	2,955	2,799
Expected return on plan assets	(3,131)	(3,249)
Amortization of prior service cost	4	9
Recognized actuarial loss	1,027	283
Net periodic benefit cost	2,657	2,470
Other Benefits
Components of the net periodic benefit cost
Service cost	12	119
Interest cost	114	320
Amortization of prior service cost	(844)	(303)
Recognized actuarial loss	246	166
Net periodic benefit cost	$ (472)	$ 302