Income Taxes (Differences Between Effective Rates And Statutory Federal Income Tax Rate Computed On Income Before Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Federal income tax expense computed at statutory Federal rate, Amount			$ 16,932	$ 25,337	$ 30,392
Federal income tax expense computed at statutory Federal rate, Percentage	35.00%	21.00%	21.00%	21.00%		24.50%	24.50%
Increases (Decreases) In Taxes Resulting From:
State taxes, net of Federal tax effect, Amount			$ 2,626	$ 4,024	3,986
State taxes, net of Federal tax effect, Percentage			3.30%	3.30%			3.20%
Deferred tax liability remeasurement, net, Amount			$ 0	$ 0	(7,498)
Deferred tax liability remeasurement, net, Percentage			0	0			(0.060)
Low income housing tax credits, net, Amount			$ (1,897)	$ (1,745)	(500)
Low income housing tax credits, net, Percentage			(2.40%)	(1.40%)			(0.40%)
ESOP related expenses, net, Amount			$ (525)	$ (757)	(790)
ESOP related expenses, net, Percentage			(0.60%)	(0.60%)			(0.60%)
Acquired BOLI policies, Amount			$ (636)	$ 0	0
Acquired BOLI policies, Percentage			(0.80%)	0.00%			0.00%
Other, Amount			$ (410)	$ (448)	(611)
Other, Percentage			(0.50%)	(0.40%)			(0.50%)
Income tax expense			$ 16,090	$ 26,411	$ 24,979
Income tax expense, Percentage			20.00%	21.90%			20.20%