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
Revenue recognition
Increase (decrease) in operating income	$ (44,055)	$ 26,905	$ 37,376	$ 20,509	$ 30,740	$ 39,602	$ 35,923	$ 29,940	$ 40,735	$ 136,205	$ 118,583
Increase (decrease) in net income	(37,152)	18,405	29,702	14,314	21,967	27,448	25,907	22,309	25,269	97,631	86,354
Increase (decrease) in net income per common share (in dollars per share)	$ (1.39)	$ 0.69	$ 1.11	$ 0.53	$ 0.82	$ 1.02	$ 0.97	$ 0.83	$ 0.94	$ 3.64	$ 3.22
Change in estimated total costs | Adjustment
Revenue recognition
Increase (decrease) in operating income	(9,900)				700				(1,700)	15,700	173,000
Increase (decrease) in net income	$ (6,600)				$ 300				$ (300)	$ 10,700	$ 11,700
Increase (decrease) in net income per common share (in dollars per share)	$ (0.25)				$ 0.01				$ (0.01)	$ 0.40	$ 0.44