Business Combinations - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Net income	$ 5,615	$ 3,614
Basic (in dollars per share)	$ 0.68	$ 0.49
Diluted (in dollars per share)	$ 0.66	$ 0.48
Pro Forma | South Sound Merger
Business Acquisition [Line Items]
Total revenues (net interest income plus non-interest income)	$ 15,610	$ 14,362
Net income	$ 5,666	$ 3,789
Basic (in dollars per share)	$ 0.68	$ 0.46
Diluted (in dollars per share)	$ 0.67	$ 0.45