Variable Interest Entities - Net assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
ASSETS
Total assets	$ 2,273,690		$ 2,273,690		$ 1,847,170
LIABILITIES AND SHAREHOLDERS' EQUITY
Shareholders' equity related to Cubic	895,804		895,804		961,649
Noncontrolling interest in VIE	9,731		9,731		18,919
Total liabilities and shareholders' equity	2,273,690		2,273,690		1,847,170
Revenue	321,482	$ 337,339	650,321	$ 642,598
Operating income (loss)	(29,934)	(6,541)	(36,417)	(7,107)
Other income (expense), net	(19,664)	(3,602)	(19,791)	(8,355)
VIE
ASSETS
Cash	457		457		347
Restricted cash	9,967		9,967		9,967
Other current assets	112		112		33
Long-term contracts financing receivables	137,870		137,870		115,508
Other noncurrent assets					1,419
Total assets	148,406		148,406		127,274
LIABILITIES AND SHAREHOLDERS' EQUITY
Trade accounts payable					25
Accrued compensation and other current liabilities	181		181		191
Due to Cubic	19,220		19,220		25,143
Other noncurrent liabilities	33,087		33,087		21,605
Long-term debt	87,814		87,814		61,994
Total liabilities	140,302		140,302		108,958
Shareholders' equity related to Cubic	(1,627)		(1,627)		(603)
Noncontrolling interest in VIE	9,731		9,731		18,919
Total liabilities and shareholders' equity	148,406		148,406		$ 127,274
Revenue	1,802	2,325	3,047	4,286
Operating income (loss)	1,516	2,030	2,488	3,698
Other income (expense), net	(15,819)	(3,720)	(12,748)	(9,863)
Interest income	1,655	757	3,208	1,260
Interest Expense	$ (1,995)	$ (598)	$ (3,154)	$ (1,110)