SUMMARY OF QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Summary Of quarterly results of operations
Increase (decrease) in operating income	$ (43,507)	$ 27,009	$ 34,648	$ 18,242	$ 29,142	$ 38,586	$ 32,540	$ 27,754	$ 36,392	$ 128,022	$ 113,508
Increase (decrease) in net income									19,981	92,104	83,904
Increase (decrease) in net income per common share (in dollars per share)	$ (1.43)	$ 0.69	$ 1.02	$ 0.47	$ 0.79	$ 1.00	$ 0.88	$ 0.77	$ 0.74	$ 3.44	$ 3.13
Change in estimated total costs | Adjustment
Summary Of quarterly results of operations
Increase (decrease) in operating income	(10,400)				2,300				(2,800)	17,500	17,000
Increase (decrease) in net income	$ (6,900)				$ 1,500				$ (1,100)	$ 12,000	$ 11,500
Increase (decrease) in net income per common share (in dollars per share)	$ 0.26				$ 0.06				$ 0.04	$ 0.45	$ 0.43