Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative effect of adopting Accounting Standards Update ("ASU") 2016-13 ("CECL"), net of tax [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Unearned Compensation ESOP [Member]	Retained Earnings [Member]	Retained Earnings [Member] Cumulative effect of adopting Accounting Standards Update ("ASU") 2016-13 ("CECL"), net of tax [Member]	AOCI [Member]
Balance at Sep. 30, 2020	$ 1,284,859		$ 1,389	$ 1,189,853	$ (33,040)	$ 143,162		$ (16,505)
Balance (Accounting Standards Update 2016-13 [Member]) at Sep. 30, 2020		$ (2,288)					$ (2,288)
Net income	18,898					18,898
Other comprehensive income (loss), net of tax	5,134							5,134
ESOP activity	493			80	413
Restricted stock activity, net	(8)			(8)
Stock-based compensation	118			118
Repurchase of common stock	(1,530)		(1)	(1,407)		(122)
Cash dividends to stockholders	(29,128)					(29,128)
Balance at Dec. 31, 2020	1,276,548		1,388	1,188,636	(32,627)	130,522		(11,371)
Balance at Sep. 30, 2020	1,284,859		1,389	1,189,853	(33,040)	143,162		(16,505)
Balance (Accounting Standards Update 2016-13 [Member]) at Sep. 30, 2020		$ (2,288)					$ (2,288)
Net income	57,529
Other comprehensive income (loss), net of tax								3,167
Balance at Jun. 30, 2021	1,237,624		1,388	1,189,466	(31,801)	91,909		(13,338)
Balance at Dec. 31, 2020	1,276,548		1,388	1,188,636	(32,627)	130,522		(11,371)
Net income	20,444					20,444
Other comprehensive income (loss), net of tax	(7,582)							(7,582)
ESOP activity	545			132	413
Stock-based compensation	134			134
Stock options exercised	24			24
Cash dividends to stockholders	(11,518)					(11,518)
Balance at Mar. 31, 2021	1,278,595		1,388	1,188,926	(32,214)	139,448		(18,953)
Net income	18,187					18,187
Other comprehensive income (loss), net of tax	5,615							5,615
ESOP activity	531			118	413
Restricted stock activity, net	(5)			(5)
Stock-based compensation	127			127
Stock options exercised	300			300
Cash dividends to stockholders	(65,726)					(65,726)
Balance at Jun. 30, 2021	1,237,624		1,388	1,189,466	(31,801)	91,909		(13,338)
Balance at Sep. 30, 2021	1,242,273		1,388	1,189,633	(31,387)	98,944		(16,305)
Net income	22,186					22,186
Other comprehensive income (loss), net of tax	(7,021)							(7,021)
ESOP activity	487			74	413
Restricted stock activity, net	(3)			(3)
Stock-based compensation	123			123
Cash dividends to stockholders	(41,385)					(41,385)
Balance at Dec. 31, 2021	1,216,660		1,388	1,189,827	(30,974)	79,745		(23,326)
Balance at Sep. 30, 2021	1,242,273		1,388	1,189,633	(31,387)	98,944		(16,305)
Net income	64,961
Other comprehensive income (loss), net of tax								(85,620)
Balance at Jun. 30, 2022	1,131,740		1,388	1,190,117	(30,148)	72,308		(101,925)
Balance at Dec. 31, 2021	1,216,660		1,388	1,189,827	(30,974)	79,745		(23,326)
Net income	21,623					21,623
Other comprehensive income (loss), net of tax	(52,581)							(52,581)
ESOP activity	461			48	413
Stock-based compensation	124			124
Cash dividends to stockholders	(11,535)					(11,535)
Balance at Mar. 31, 2022	1,174,752		1,388	1,189,999	(30,561)	89,833		(75,907)
Net income	21,152					21,152
Other comprehensive income (loss), net of tax	(26,018)							(26,018)
ESOP activity	408			(5)	413
Restricted stock activity, net	(3)			(3)
Stock-based compensation	126			126
Cash dividends to stockholders	(38,677)					(38,677)
Balance at Jun. 30, 2022	$ 1,131,740		$ 1,388	$ 1,190,117	$ (30,148)	$ 72,308		$ (101,925)