Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Business Acquisition [Line Items]
Net income	$ 5,049	$ 6,114	$ 11,701	$ 11,729
Basic net income per common share (in dollars per share)	$ 0.61	$ 0.74	$ 1.40	$ 1.41
Diluted net income per common share (in dollars per share)	$ 0.60	$ 0.72	$ 1.38	$ 1.39