Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020		Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period		$ 178,008	$ 162,338	$ 171,067	[1]	$ 124,657
Balance at end of period		182,806	166,269	182,806		166,269
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(179)	(45)	50		(129)
Other comprehensive (loss) income	[2]	155	12	(74)		33
Balance at end of period	[2]	(24)	(33)	(24)		(33)
Accumulated Net Unrealized Investment Gain (Loss) | Available-for-sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(151)	3	90		(58)
Other comprehensive (loss) income	[2]	154	9	(87)		7
Balance at end of period	[2]	3	12	3		12
Accumulated Net Unrealized Investment Gain (Loss) | Held-to-maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at beginning of period	[2]	(28)	(48)	(40)		(71)
Other comprehensive (loss) income	[2]	1	3	13		26
Balance at end of period	[2]	$ (27)	$ (45)	$ (27)		(45)
Accounting Standards Update 2016-01
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive (loss) income						63
Accounting Standards Update 2016-01 | Accumulated Net Unrealized Investment Gain (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive (loss) income						63
Accounting Standards Update 2016-01 | Accumulated Net Unrealized Investment Gain (Loss) | Held-to-maturity Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Other comprehensive (loss) income						$ 0

[1] Derived from audited consolidated financial statements.

[2] All amounts are net of income taxes.