Consolidated Balance Sheets (Parenthetical) - £ / shares shares in Thousands	Sep. 30, 2025	Sep. 30, 2024
Statement of Financial Position [Abstract]
Preferred Shares, authorized	25,000	25,000
Preferred Shares, par value	£ 0.01	£ 0.01
Preferred Shares, issued	0	0
Preferred Shares, outstanding	0	0
Ordinary Shares, authorized	700,000	700,000
Ordinary Shares, par value	£ 0.01	£ 0.01
Ordinary Shares, issued	290,351	288,485
Ordinary Shares, outstanding	108,448	112,891
Treasury stock	181,903	175,594

Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Number of shares issued for nonredeemable preferred shares and preferred shares redeemable solely at option of issuer. Includes, but is not limited to, preferred shares issued, repurchased, and held as treasury shares. Excludes preferred shares classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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Number of previously issued common shares repurchased by the issuing entity and held in treasury.

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