Basis for Presentation - ASC 606 (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Oct. 01, 2018	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition
Equity	$ 965,582		$ 965,582		$ 748,685	$ 724,196
Operating income (loss)	34,725	$ 10,290	27,618	$ (3,291)
Net income (loss) from continuing operations	$ 20,546	$ (970)	$ 502	$ (15,751)
Diluted earnings per share attributable to Cubic (in dollars per share)	$ 0.77	$ 0.23	$ 0.26	$ (0.20)
ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Equity	$ 40,863		$ 40,863			$ 24,489
Operating income (loss)	3,638		12,362
Net income (loss) from continuing operations	$ 5,379		$ 16,374
Diluted earnings per share attributable to Cubic (in dollars per share)	$ 0.06		$ 0.28
ASU 2014-09 | ASC 606 | Change in Estimates
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)	$ (1,054)	$ 2,239	$ (1,040)	$ 114
Net income (loss) from continuing operations	$ (1,185)	$ 1,739	$ (1,100)	$ 109
Diluted earnings per share attributable to Cubic (in dollars per share)	$ (0.04)	$ 0.06	$ (0.04)
ASU 2014-09 | Adjustments
Revenue, Initial Application Period Cumulative Effect Transition
Equity					$ 24,500