Discontinued operations - Discontinued operations results of operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Revenue	$ 9,615	$ 8,948	$ 18,438	$ 17,250
Cost of operations	6,106	6,789	8,329	12,746
Interest expense	(415)	(620)	(896)	(1,065)
Provision for income taxes	1,189	541	6,068	1,263
Income from discontinued operations	0	516	0	2,179
Patriot Transportation
Revenue	0	10,083	0	41,800
Cost of operations	0	9,230	0	38,195
Operating profit	0	853	0	3,605
Interest expense	0	(7)	0	(33)
Income before income taxes	0	846	0	3,572
Provision for income taxes	0	330	0	1,393
Income from discontinued operations	$ 0	$ 516	$ 0	$ 2,179