Variable Interest Entities - Net assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Oct. 01, 2018
ASSETS
Restricted cash		$ 11,800	$ 27,400
Long-term contracts financing receivables			6,134
Other noncurrent assets	$ 13,871
Total assets	1,548,955		1,304,883	$ 1,321,130
LIABILITIES AND SHAREHOLDERS' EQUITY
Total Cubic equity	926,504		700,121	719,955
Noncontrolling interests	24,703		24,075	28,730
Total liabilities and shareholders' equity	1,548,955		1,304,883	1,321,130
Revenue	305,259	248,391
Operating income (loss)	(566)	(11,902)
Other income (expense), net	(4,753)	$ (78)
OpCo.
ASSETS
Cash	421		374	374
Restricted cash	10,000		10,000	10,000
Long-term capitalized contract costs			1,258
Long-term contracts financing receivables	52,996			38,990
Other noncurrent assets	962		810	810
LIABILITIES AND SHAREHOLDERS' EQUITY
Trade accounts payable	205		165	165
Other long term liabilities	6,146		13	13
Long-term debt	15,357		9,056	$ 9,056
VIE
ASSETS
Cash	421		374
Restricted cash	10,000		10,000
Long-term capitalized contract costs			1,258
Long-term contracts financing receivables	52,996
Other noncurrent assets	962		810
Total assets	64,379		12,442
LIABILITIES AND SHAREHOLDERS' EQUITY
Trade accounts payable	205		165
Other long term liabilities	6,146		13
Long-term debt	15,357		9,056
Total liabilities	21,708		9,234
Total Cubic equity	39		(304)
Noncontrolling interests	24,703		24,348
Total liabilities and shareholders' equity	46,450		33,278
Revenue			1,961
Operating income (loss)			1,668
Other income (expense), net			(6,133)
Interest income			503
Interest Expense			(512)
VIE | Consolidation Eliminations
ASSETS
Total assets			$ 20,800
LIABILITIES AND SHAREHOLDERS' EQUITY
Total liabilities	$ 17,900