GOODWILL AND PURCHASED INTANGIBLE ASSETS - Goodwill (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) item
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 237,899	$ 184,141
Acquisitions	175,150	57,875
Foreign currency exchange rate changes	(6,103)	(4,117)
Balance at the end of the period	406,946	237,899
Components of net goodwill
Goodwill			$ 457,811
Accumulated impairment charges			(50,865)
Net balances	237,899	184,141	$ 406,946
Number of remaining reporting units whose estimated fair values exceeded carrying values | item			3
Impairment of goodwill	0
Cubic Transportation Systems
Changes in the carrying amount of goodwill
Balance at the beginning of the period	55,974	59,167
Foreign currency exchange rate changes	(6,344)	(3,193)
Balance at the end of the period	49,630	55,974
Components of net goodwill
Goodwill			$ 49,630
Net balances	$ 55,974	59,167	49,630
Cubic Transportation Systems | Minimum
Components of net goodwill
Estimated percentage of excess of fair value over carrying value	20.00%
Cubic Global Defense Systems
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 87,575	30,624
Acquisitions	175,150	57,875
Foreign currency exchange rate changes	241	(924)
Balance at the end of the period	262,966	87,575
Components of net goodwill
Goodwill			262,966
Net balances	$ 87,575	30,624	262,966
Cubic Global Defense Systems | Minimum
Components of net goodwill
Estimated percentage of excess of fair value over carrying value	20.00%
Cubic Global Defense Services
Changes in the carrying amount of goodwill
Balance at the beginning of the period	$ 94,350	94,350
Acquisitions
Foreign currency exchange rate changes
Balance at the end of the period	94,350	94,350
Components of net goodwill
Goodwill			145,215
Accumulated impairment charges			(50,865)
Net balances	$ 94,350	$ 94,350	$ 94,350
Cubic Global Defense Services | Minimum
Components of net goodwill
Estimated percentage of excess of fair value over carrying value	15.00%