Segment Information - Business Segment Financial Data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Segment Information
Sales	$ 321,482	$ 337,339	$ 650,321	$ 642,598
Operating income (loss)	(29,934)	(6,541)	(36,417)	(7,107)
Depreciation and amortization	23,414	17,587	40,364	33,598
Cubic Transportation Systems
Segment Information
Sales	197,600	200,700	386,200	382,500
Operating income (loss)	12,600	8,800	26,900	19,800
Depreciation and amortization	7,400	9,500	14,500	17,200
Cubic Mission Solutions
Segment Information
Sales	39,500	61,900	98,200	108,300
Operating income (loss)	(31,400)	(8,500)	(46,300)	(13,400)
Depreciation and amortization	13,500	5,800	21,000	11,200
Cubic Global Defense Systems
Segment Information
Sales	84,400	74,700	165,900	151,800
Operating income (loss)	5,700	5,200	12,000	8,100
Depreciation and amortization	1,600	1,500	3,300	3,700
Corporate
Segment Information
Depreciation and amortization	900	800	1,600	1,500
Unallocated corporate expenses and other
Segment Information
Operating income (loss)	$ (16,800)	$ (12,000)	$ (29,000)	$ (21,600)