Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Loans Receivable And Allowance For Credit Losses (Summary Of Loan Portfolio Segment Disaggregated By The Company's Impairment Method) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	$ 7,395,579		$ 7,404,179
Recorded investment in loans individually evaluated for impairment	23,726		21,794
Financing receivable, total recorded investment	7,419,305		7,425,973
ACL for loans collectively evaluated for impairment	30,975		9,226
ACL for loans individually evaluated for impairment	240		0
ACL	31,215	$ 31,196	9,226	$ 9,036	$ 8,619	$ 8,463
One- to Four-Family Segment [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	6,474,563		6,509,292
Recorded investment in loans individually evaluated for impairment	19,830		21,389
Financing receivable, total recorded investment	6,494,393		6,530,681
ACL for loans collectively evaluated for impairment	10,041		3,890
ACL for loans individually evaluated for impairment	0		0
ACL	10,041	10,379	3,890	4,053	4,367	5,739
One- to Four-Family Segment [Member] \| Originated [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	3,964,815		3,881,100
Recorded investment in loans individually evaluated for impairment	13,306		14,683
Financing receivable, total recorded investment	3,978,121		3,895,783
ACL for loans collectively evaluated for impairment	6,346		2,000
ACL for loans individually evaluated for impairment	0		0
ACL	6,346	6,467	2,000	2,036	2,173	2,953
One- to Four-Family Segment [Member] \| Correspondent Purchased [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	2,295,684		2,379,651
Recorded investment in loans individually evaluated for impairment	1,951		1,763
Financing receivable, total recorded investment	2,297,635		2,381,414
ACL for loans collectively evaluated for impairment	3,189		1,203
ACL for loans individually evaluated for impairment	0		0
ACL	3,189	3,355	1,203	1,275	1,392	1,861
One- to Four-Family Segment [Member] \| Bulk Purchased [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	214,064		248,541
Recorded investment in loans individually evaluated for impairment	4,573		4,943
Financing receivable, total recorded investment	218,637		253,484
ACL for loans collectively evaluated for impairment	506		687
ACL for loans individually evaluated for impairment	0		0
ACL	506	557	687	742	802	925
Commercial Segment [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	804,213		763,662
Recorded investment in loans individually evaluated for impairment	3,607		60
Financing receivable, total recorded investment	807,820		763,722
ACL for loans collectively evaluated for impairment	20,464		5,171
ACL for loans individually evaluated for impairment	240		0
ACL	20,704	20,328	5,171	4,832	4,088	2,556
Consumer Segment [Member]
Financing Receivable, Impaired [Line Items]
Recorded investment in loans collectively evaluated for impairment	116,803		131,225
Recorded investment in loans individually evaluated for impairment	289		345
Financing receivable, total recorded investment	117,092		131,570
ACL for loans collectively evaluated for impairment	470		165
ACL for loans individually evaluated for impairment	0		0
ACL	$ 470	$ 489	$ 165	$ 151	$ 164	$ 168