Dividend (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
	May 04, 2017	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
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)		$ 2,752		$ 5,505	$ 5,492