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, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Summary Of quarterly results of operations
Increase (decrease) in operating income	$ 39,268	$ 19,215	$ 22,177	$ 11,830	$ (44,055)	$ 26,905	$ 37,376	$ 20,509	$ 92,490	$ 40,735	$ 136,205
Increase (decrease) in net income									69,580	25,269	97,631
Increase (decrease) in net income per common share (in dollars per share)	$ 1.22	$ 0.46	$ 0.60	$ 0.31	$ (1.39)	$ 0.69	$ 1.11	$ 0.53	$ 2.59	$ 0.94	$ 3.64
Change in estimated total costs | Adjustment
Summary Of quarterly results of operations
Increase (decrease) in operating income	(10,700)				9,900				1,300	1,700	15,700
Increase (decrease) in net income	$ (7,600)				$ 6,600				$ (3,500)	$ 300	$ 10,700
Increase (decrease) in net income per common share (in dollars per share)	$ (0.28)				$ 0.25				$ 0.13	$ 0.01	$ 0.40