Summary of Quarterly Results of Operations (Unaudited)) - Impact (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)	$ 58,619	$ 34,725	$ (6,541)	$ (566)	$ 27,673	$ 10,290	$ (1,679)	$ (11,902)	$ 86,237	$ 24,382	$ 2,628
Net income (loss) from continuing operations									$ 41,306	$ 7,793	$ (25,740)
Diluted earnings per share attributable to Cubic (in dollars per share)	$ 1.38	$ 0.77	$ (0.30)	$ (0.23)	$ 0.65	$ 0.23	$ (0.07)	$ (0.36)	$ 1.62	$ 0.45	$ (0.41)
ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)									$ 14,885
Net income (loss) from continuing operations									$ 21,029
Diluted earnings per share attributable to Cubic (in dollars per share)									$ 0.29
ASU 2014-09 | ASC 606 | Change in Estimates
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)	$ (1,420)				$ (4,162)				$ (2,235)	$ (6,986)	$ 5,737
Net income (loss) from continuing operations	$ (1,615)				$ (3,149)				$ (2,351)	$ (5,146)	$ 3,208
Diluted earnings per share attributable to Cubic (in dollars per share)	$ (0.05)				$ (0.12)				$ (0.08)	$ (0.19)	$ 0.12