Summary Of Significant Accounting Policies (Cumulative-Effect Adjustment) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Summary Of Significant Accounting Policies [Line Items]
ACL	$ 23,397	$ 26,125	$ 31,527	$ 31,196	$ 9,435	$ 9,226
Reserve for off-balance sheet credit exposures	6,127	6,433	0
ACL and Reserve for Off-Balance Sheet Credit Exposures			31,527
Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(4,761)
Reserve for off-balance sheet credit exposures			7,788
ACL and Reserve for Off-Balance Sheet Credit Exposures			3,027
Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			26,766
Reserve for off-balance sheet credit exposures			7,788
ACL and Reserve for Off-Balance Sheet Credit Exposures			34,554
One- to Four-Family Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	3,988	4,148	9,243	10,379	3,859	3,890
One- to Four-Family Segment [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(4,383)
One- to Four-Family Segment [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			4,860
One- to Four-Family Segment [Member] | Originated [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	1,536	1,538	6,085	6,467	2,047	2,000
One- to Four-Family Segment [Member] | Originated [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(4,452)
One- to Four-Family Segment [Member] | Originated [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			1,633
One- to Four-Family Segment [Member] | Correspondent Purchased [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	1,705	1,758	2,691	3,355	1,200	1,203
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(367)
One- to Four-Family Segment [Member] | Correspondent Purchased [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			2,324
One- to Four-Family Segment [Member] | Bulk Purchased [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	747	852	467	557	612	687
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			436
One- to Four-Family Segment [Member] | Bulk Purchased [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			903
Commercial Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	19,157	21,707	21,800	20,328	5,418	5,171
Commercial Segment [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(193)
Commercial Segment [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			21,607
Commercial Segment [Member] | Commercial Real Estate [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			20,349
Commercial Segment [Member] | Commercial Real Estate [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			699
Commercial Segment [Member] | Commercial Real Estate [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			21,048
Commercial Segment [Member] | Commercial and Industrial [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			1,451
Commercial Segment [Member] | Commercial and Industrial [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(892)
Commercial Segment [Member] | Commercial and Industrial [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			559
Consumer Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL	$ 252	$ 270	484	$ 489	$ 158	$ 165
Consumer Segment [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(185)
Consumer Segment [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			299
Consumer Segment [Member] | Home Equity [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			370
Consumer Segment [Member] | Home Equity [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			(289)
Consumer Segment [Member] | Home Equity [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			81
Consumer Segment [Member] | Other [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			114
Consumer Segment [Member] | Other [Member] | Cumulative effect adjustment - Adoption of CECL [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			104
Consumer Segment [Member] | Other [Member] | Balance at October 1, 2020 [Member] | Accounting Standards Update 2016-13 [Member]
Summary Of Significant Accounting Policies [Line Items]
ACL			$ 218