Securities (Schedule Of Carrying Value Of Securities Pledged As Collateral) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Sep. 30, 2021
Marketable Securities [Abstract]
Public unit deposits	$ 210,887	$ 264,885
Federal Reserve Bank of Kansas City ("FRB of Kansas City")	57,246	64,707
Commercial deposits	22,325	66,256
Total securities pledged as collateral	$ 290,458	$ 395,848

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for commercial deposits, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

No definition available.

+ Details

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Balance Type:	debit
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- Definition

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for public unit deposits, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

+ References

No definition available.

+ Details

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Namespace Prefix:	cffn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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Balance Type:	na
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- Definition

The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for debt facilities other than FHLB loans, repurchase agreements and letter of credit arrangements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

+ Details

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