SUMMARY OF QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (Details 16) (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
Interim Financial Information
Revenue recognition
Increase (decrease) in operating income	(44,100)	26,900	37,400	20,500	30,700	39,600	35,900	29,900
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
Change in estimated total costs | Interim Financial Information
Revenue recognition
Increase (decrease) in operating income	(9,800)	1,900	3,500	300	700	12,600	7,200	1,200
Increase (decrease) in net income	$ (6,600)	$ 900	$ 2,800	$ 500	$ 350	$ 8,100	$ 5,000	$ 900
Increase (decrease) in net income per common share (in dollars per share)	$ (0.25)	$ 0.03	$ 0.11	$ 0.02	$ 0.01	$ 0.30	$ 0.19	$ 0.03