RETIREMENT PLANS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plan [Member]
Components of net periodic benefit cost: [Abstract]
Service cost	$ 3,243	$ 2,539	$ 6,414	$ 5,105
Interest cost	2,867	2,670	5,702	5,254
Expected return on plan assets	(4,039)	(3,218)	(8,066)	(6,438)
Amortization of actuarial gain	2,083	1,946	4,139	3,698
Net periodic benefit cost	4,154	3,937	8,189	7,619
SERP [Member]
Components of net periodic benefit cost: [Abstract]
Service cost	0	0	0	0
Interest cost	18	19	35	37
Expected return on plan assets	0	0	0	0
Amortization of actuarial gain	4	3	9	7
Net periodic benefit cost	22	22	44	44
Other Postretirement Benefits [Member]
Components of net periodic benefit cost: [Abstract]
Service cost	0	0	0	0
Interest cost	28	34	56	67
Amortization of actuarial gain	(153)	(156)	(308)	(310)
Net periodic benefit cost	$ (125)	$ (122)	$ (252)	$ (243)