Variable Interest Entities - Net assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
ASSETS
Other noncurrent assets	$ 34,789		$ 21,759
Total assets	2,299,598		2,324,221
LIABILITIES AND SHAREHOLDERS' EQUITY
Shareholders' equity related to Cubic	960,758		960,777
Noncontrolling interest in VIE	33,120		27,403
Total liabilities and shareholders' equity	2,299,598		2,324,221
Revenue	318,794	$ 328,839
Operating income (loss)	1,297	(6,483)
Other income (expense), net	1,296	(127)
VIE
ASSETS
Cash	1,337		1,065
Restricted cash	3,822		1,822
Other current assets	34		31
Long-term contracts financing receivables	241,814		221,245
Total assets	247,007		224,163
LIABILITIES AND SHAREHOLDERS' EQUITY
Trade accounts payable	23		49
Accrued compensation and other current liabilities	100		85
Due to Cubic	22,674		27,259
Other noncurrent liabilities	2,638		5,890
Long-term debt	187,688		163,348
Total liabilities	213,123		196,631
Shareholders' equity related to Cubic	764		129
Noncontrolling interest in VIE	33,120		27,403
Total liabilities and shareholders' equity	247,007		$ 224,163
Revenue	4,021	1,245
Operating income (loss)	3,717	972
Other income (expense), net	3,252	3,071
Interest income	1,373	1,553
Interest Expense	$ (1,989)	$ (1,159)