EMPLOYEE BENEFIT PLANS - DEFINED BENEFIT PLANS (Details) (USD $)	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		1 Months Ended
	Mar. 31, 2013 Pension [Member]	Mar. 31, 2012 Pension [Member]	Mar. 31, 2013 Pension [Member]	Mar. 31, 2012 Pension [Member]	Mar. 31, 2013 OPEB [Member]	Mar. 31, 2012 OPEB [Member]	Mar. 31, 2013 OPEB [Member]	Mar. 31, 2012 OPEB [Member]	Dec. 31, 2012 Pension Plans Excluding Pension Equalization Plan, Defined Benefit [Member]	Dec. 31, 2011 Pension Plans Excluding Pension Equalization Plan, Defined Benefit [Member]
Components of net periodic cost
Service cost	$ 1,718,000	$ 1,344,000	$ 3,436,000	$ 2,688,000	$ 1,171,000	$ 896,000	$ 2,342,000	$ 1,792,000
Interest cost	2,235,000	2,206,000	4,470,000	4,412,000	1,287,000	1,283,000	2,574,000	2,566,000
Expected return on plan assets	(3,706,000)	(3,171,000)	(7,412,000)	(6,342,000)	(913,000)	(686,000)	(1,826,000)	(1,372,000)
Recognized actuarial loss	1,911,000	1,254,000	3,822,000	2,508,000	964,000	724,000	1,928,000	1,448,000
Prior service cost amortization	27,000	11,000	54,000	22,000	7,000	6,000	14,000	12,000
Recognized net initial obligation	0	0	0	0	(89,000)	89,000	(178,000)	178,000
Net periodic cost	2,185,000	1,644,000	4,370,000	3,288,000	2,427,000	2,312,000	4,854,000	4,624,000
Defined benefit plan, contributions by employer									$ 20,000,000	$ 20,000,000