v3.25.1

Stockholders' equity - Narrative (Details) - USD ($)	Jan. 31, 2025	Sep. 30, 2024
Share Repurchase Program [Line Items]
Share repurchase program, authorized amount		$ 300,000,000
Remaining authorized repurchase amount	$ 177,800,000
Passive Custodial Funds
Share Repurchase Program [Line Items]
Minimum net worth above custodial assets (as a percent)	2.00%
Non-passive Custodial Fund
Share Repurchase Program [Line Items]
Minimum net worth above custodial assets (as a percent)	4.00%

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- Definition

Minimum Net Worth Above Custodial Assets

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481520/505-30-50-4

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- Definition

Amount authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481520/505-30-50-4

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- Definition

Amount remaining authorized for purchase of share under share repurchase plan. Includes, but is not limited to, repurchase of stock and unit of ownership.

+ References

No definition available.

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