Mortgage Servicing Rights - Mortgage Servicing Rights (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	$ 0
Net book value at end of period	1,886	$ 0
Fair value of MSR asset at end of period	1,951	0
Mortgage servicing rights
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	0	0
MSR asset acquired	1,909	0
MSRs capitalized	13	0
Amortization during the period	(36)	0
Valuation allowance at end of period	0	0
Net book value at end of period	1,886	0
Fair value of MSR asset at end of period	1,951	0
Residential mortgage loans serviced for others	$ 282,392	$ 0
Net book value of MSR asset to loans serviced for others	0.67%