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, 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)