Investment Securities - Held To Maturity Securities, Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value, Less than 12 months	$ 35,976	$ 8,309
Fair Value, 12 Months or More	20,386	4,969
Fair Value, Total	56,362	13,278
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] [Abstract]
Unrealized Loss, Less than 12 Months	411	12
Unrealized Loss, 12 Months or More	547	43
Unrealized Loss, Total	958	55
U.S. government agency obligations
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value, Less than 12 months	8,296	4,039
Fair Value, 12 Months or More	6,932	2,494
Fair Value, Total	15,228	6,533
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] [Abstract]
Unrealized Loss, Less than 12 Months	186	4
Unrealized Loss, 12 Months or More	262	25
Unrealized Loss, Total	448	29
Obligations of states and political subdivisions
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value, Less than 12 months	8,170	2,885
Fair Value, 12 Months or More	3,701	1,338
Fair Value, Total	11,871	4,223
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] [Abstract]
Unrealized Loss, Less than 12 Months	62	7
Unrealized Loss, 12 Months or More	70	15
Unrealized Loss, Total	132	22
Mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value, Less than 12 months	14,167	1,385
Fair Value, 12 Months or More	9,753	1,137
Fair Value, Total	23,920	2,522
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] [Abstract]
Unrealized Loss, Less than 12 Months	96	1
Unrealized Loss, 12 Months or More	215	3
Unrealized Loss, Total	311	$ 4
Corporate debt securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Fair Value, Less than 12 months	5,343
Fair Value, 12 Months or More	0
Fair Value, Total	5,343
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] [Abstract]
Unrealized Loss, Less than 12 Months	67
Unrealized Loss, 12 Months or More	0
Unrealized Loss, Total	$ 67