Variable Interest Entities - Net assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2019
ASSETS
Total assets	$ 2,261,812		$ 2,261,812		$ 1,847,170
LIABILITIES AND SHAREHOLDERS' EQUITY
Shareholders' equity related to Cubic	892,863		892,863		961,649
Noncontrolling interest in VIE	20,992		20,992		18,919
Total liabilities and shareholders' equity	2,261,812		2,261,812		1,847,170
Revenue	350,439	$ 382,679	1,000,760	$ 1,025,277
Operating income (loss)	24,706	34,725	(11,711)	27,618
Other income (expense), net	(6,773)	(8,714)	(26,564)	(17,069)
VIE
ASSETS
Cash	743		743		347
Restricted cash	1,669		1,669		9,967
Other current assets	99		99		33
Long-term contracts financing receivables	191,042		191,042		115,508
Other noncurrent assets					1,419
Total assets	193,553		193,553		127,274
LIABILITIES AND SHAREHOLDERS' EQUITY
Trade accounts payable	175		175		25
Accrued compensation and other current liabilities	150		150		191
Due to Cubic	11,754		11,754		25,143
Other noncurrent liabilities	5,572		5,572		21,605
Long-term debt	155,493		155,493		61,994
Total liabilities	173,144		173,144		108,958
Shareholders' equity related to Cubic	(583)		(583)		(603)
Noncontrolling interest in VIE	20,992		20,992		18,919
Total liabilities and shareholders' equity	193,553		193,553		$ 127,274
Revenue	17,585	3,233	20,632	7,519
Operating income (loss)	17,344	2,823	19,832	6,521
Other income (expense), net	(6,888)	(7,031)	(19,636)	(16,884)
Interest income	1,663	1,075	4,871	2,335
Interest Expense	$ (1,710)	$ (829)	$ (4,864)	$ (1,939)