New Accounting Standards Implemented - Impact on segment net sales and operating income (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	$ 305,259	$ 248,391
Operating income (loss)	(566)	(11,902)
ASU 2014-09 | ASC 605
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	276,824
Operating income (loss)	(3,897)
ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	28,435		$ 114,900
Operating income (loss)	3,331
Unallocated corporate expenses and other
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)	(9,499)	(14,300)
Unallocated corporate expenses and other | ASU 2014-09 | ASC 605
Revenue, Initial Application Period Cumulative Effect Transition
Operating income (loss)	(9,499)
Transportation Systems
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	181,807	146,500
Operating income (loss)	10,976	9,900
Transportation Systems | ASU 2014-09 | ASC 605
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	172,728
Operating income (loss)	9,186
Transportation Systems | ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	9,079
Operating income (loss)	1,790
Cubic Mission Solutions
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	46,393	33,100
Operating income (loss)	(4,940)	(8,900)
Cubic Mission Solutions | ASU 2014-09 | ASC 605
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	45,363
Operating income (loss)	(5,191)
Cubic Mission Solutions | ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	1,030
Operating income (loss)	251
Cubic Global Defense
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	77,059	68,800
Operating income (loss)	2,897	$ 1,400
Cubic Global Defense | ASU 2014-09 | ASC 605
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	58,733
Operating income (loss)	1,607
Cubic Global Defense | ASU 2014-09 | ASC 606
Revenue, Initial Application Period Cumulative Effect Transition
Net sales	18,326
Operating income (loss)	$ 1,290