Loan Servicing Rights - Schedule of Loan Servicing Rights Activity and Valuation Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2016
Loan servicing rights
Beginning of period	$ 4,906	$ 0	$ 5,794	$ 0
Acquired in HF Financial acquisition	0	6,573	0	6,573
Additions	0	0	0	0
Amortization	(369)	(166)	(1,257)	(166)
End of period	4,537	6,407	4,537	6,407
Valuation Allowance for Impairment of Recognized Servicing Assets [Roll Forward]
Beginning of period	(3)	0	(13)	0
(Additions) / reductions	(4)	(176)	6	(176)
End of period	(7)	(176)	(7)	(176)
Loan servicing rights, net	4,530	6,231	4,530	6,231	$ 5,781
Servicing fees received	500	306	1,573	306
Balance of loans serviced at:
Beginning of period	792,779	0	868,865	0
End of period	$ 759,670	$ 914,694	$ 759,670	$ 914,694