Other Expenses - Other Expenses Breakout (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Other Expenses [Abstract]
Insurance	$ 1.0	$ 0.8
Advertising, meetings, and conferences	1.4	1.4
Office supplies and printing	0.4	0.5
Other clearing related expenses	0.8	0.4
Other non-income taxes	1.3	0.9
Other	2.6	2.5
Total other expenses	$ 7.5	$ 6.5