Acquisitions and Divestitures - CGD Services - Income (loss) from discontinued operations (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Apr. 18, 2018
Costs and expenses:
Net income from discontinued operations	$ (202)	$ 5,380		$ (1,541)	$ 8,364
Cubic Global Defense Services | Disposed of by sale
Divestitures
Consideration from sale		133,800			133,800			$ 135,000
Working capital settlement receivable						$ 1,300	$ 3,700
Receivable for estimated earn-out amount due from purchaser	3,000			3,000
Receivable for estimated amount due from purchaser	0			0
Income (loss) from discontinued operations
Net sales		71,867			262,228
Costs and expenses:
Cost of sales		64,597			235,279
Selling, general and administrative expenses		3,133			10,676
Amortization of purchased intangibles		276			1,373
Restructuring costs					7
Other income		(2)			(15)
Earnings from discontinued operations before income taxes		3,863			14,908
Net loss on sale	202	(819)	$ 6,900	1,541	6,081
Income tax provision (benefit)		(698)			463
Net income from discontinued operations	$ (202)	$ 5,380		$ (1,541)	$ 8,364