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Note 2 - Securities - Summary of Amortized Costs and Fair Values of Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020
Amortized cost, available for sale securities	$ 290,058		$ 136,355
Gross unrealized gains, available for sale securities	2,033		3,952
Gross unrealized losses, available for sale securities	(2,596)		(82)
Fair value, available for sale securities	289,495	$ 289,495	140,225
Securities held to maturity, at amortized cost (fair value, 2021, $33,617; 2020, $14,743)	33,441		14,234
Gross unrealized gains, held to maturity securities	242		509
Gross unrealized losses, held to maturity securities	(66)		0
Securities, fair value	33,617	33,617	14,743
Amortized cost, held to maturity securities	33,441		14,234
Fair value, held to maturity securities	33,617	33,617	14,743
Amortized cost	323,499		150,589
Gross unrealized gains	2,275		4,461
Gross unrealized losses	(2,662)		(82)
Total securities, fair value		323,112	154,968
US Treasury Securities [Member]
Amortized cost, available for sale securities	39,871
Gross unrealized gains, available for sale securities	37
Gross unrealized losses, available for sale securities	(250)
Fair value, available for sale securities		39,658
US Agency and Mortgage-backed Securities [Member]
Amortized cost, available for sale securities	177,131		98,848
Gross unrealized gains, available for sale securities	1,085		2,830
Gross unrealized losses, available for sale securities	(1,837)		(80)
Fair value, available for sale securities		176,379	101,598
Securities held to maturity, at amortized cost (fair value, 2021, $33,617; 2020, $14,743)	26,392		9,588
Gross unrealized gains, held to maturity securities	124		264
Gross unrealized losses, held to maturity securities	(53)		0
Securities, fair value		26,463	9,852
Amortized cost, held to maturity securities	26,392		9,588
Fair value, held to maturity securities		26,463	9,852
US States and Political Subdivisions Debt Securities [Member]
Amortized cost, available for sale securities	71,037		37,507
Gross unrealized gains, available for sale securities	910		1,122
Gross unrealized losses, available for sale securities	(509)		(2)
Fair value, available for sale securities		71,438	38,627
Securities held to maturity, at amortized cost (fair value, 2021, $33,617; 2020, $14,743)	7,049		3,146
Gross unrealized gains, held to maturity securities	118		140
Gross unrealized losses, held to maturity securities	(13)		0
Securities, fair value		7,154	3,286
Amortized cost, held to maturity securities	7,049		3,146
Fair value, held to maturity securities		7,154	3,286
Corporate Debt Securities [Member]
Securities held to maturity, at amortized cost (fair value, 2021, $33,617; 2020, $14,743)	2,019		1,500
Gross unrealized gains, held to maturity securities	1		105
Gross unrealized losses, held to maturity securities	0		0
Securities, fair value		2,020	1,605
Amortized cost, held to maturity securities	$ 2,019		1,500
Fair value, held to maturity securities		$ 2,020	$ 1,605

X

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