Dividend (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	May 03, 2018	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Common stock dividend
Dividend declared (in dollars per share)	$ 0.22	$ 0.22	$ 0.22	$ 0.44	$ 0.44
Dividend paid (in dollars per share)		$ 0.22
Dividend paid (in dollars)		$ 2,754		$ 5,509	$ 5,505
Dividend deferred in accordance with Deferred Compensation Plan		$ 4		$ 7