Acquisitions and Divestitures - CGD Services - Income (loss) from discontinued operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2018	Apr. 18, 2018
Costs and expenses:
Net income from discontinued operations	$ 4,243	$ 14,531	$ 13,815
Cubic Global Defense Services | Discontinued operations held-for-sale
Divestitures
Consideration from sale					$ 135,000
Receivable for estimated amount due from purchaser					$ 3,000
Cubic Global Defense Services | Disposed of by sale
Divestitures
Consideration from sale				$ 133,800
Receivable for estimated amount due from purchaser	3,700
Estimated selling costs	4,500
Income (loss) from discontinued operations
Net sales	262,228	378,152	391,064
Costs and expenses:
Cost of sales	235,279	342,819	350,429
Selling, general and administrative expenses	11,365	17,487	16,430
Amortization of purchased intangibles	1,373	2,752	4,764
Restructuring costs	7	208	574
Other income	(15)	(46)	(93)
Earnings from discontinued operations before income taxes	14,219	14,932	18,960
Net (gain) loss on sale	6,131
Income tax provision (benefit)	3,845	401	5,145
Net income from discontinued operations	$ 4,243	$ 14,531	$ 13,815