BUSINESS SEGMENT INFORMATION (Details 3) (USD $)	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 item	Sep. 30, 2012	Sep. 30, 2011
Revenue recognition
Increase (decrease) in operating income	$ (44,055,000)	$ 26,905,000	$ 37,376,000	$ 20,509,000	$ 30,740,000	$ 39,602,000	$ 35,923,000	$ 29,940,000	$ 40,735,000	$ 136,205,000	$ 118,583,000
Increase (decrease) in net income	(37,152,000)	18,405,000	29,702,000	14,314,000	21,967,000	27,448,000	25,907,000	22,309,000	25,269,000	97,631,000	86,354,000
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
Number of transportation systems service contracts contains annual system usage incentives									1
Sales related to annual system usage incentives									13,200,000	12,200,000	6,600,000
Change in estimated total costs | Adjustment
Revenue recognition
Increase (decrease) in operating income	(9,900,000)				700,000				(1,700,000)	15,700,000	173,000,000
Increase (decrease) in net income	$ (6,600,000)				$ 300,000				$ (300,000)	$ 10,700,000	$ 11,700,000
Increase (decrease) in net income per common share (in dollars per share)	$ (0.25)				$ 0.01				$ (0.01)	$ 0.40	$ 0.44