Number Of Executive Awards

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Share-Based Compensation Arrangement By Share-Based Payment Award, Annual Increase In Shares Authorized

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Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Cancelled In Period

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Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Fixed Monetary Award

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Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Issued In Connection With The IPO

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Share-based Compensation Arrangement By Share-Based Payment Award, Maximum Employee Subscription Amount

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Share-Based Compensation Arrangement By Share-Based Payment Award, Purchase Period

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Share-Based Payment Arrangement, Plan Modification, Cash Settlement, Shared Held By Participant

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- Definition

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due after one year (or beyond the operating cycle if longer), including liabilities for compensation costs, fringe benefits other than pension and postretirement obligations, rent, contractual rights and obligations, and statutory obligations.

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Amount of excess of issue price over par or stated value of stock and from other transaction involving stock or stockholder. Includes, but is not limited to, additional paid-in capital (APIC) for common and preferred stock.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Total of the carrying values as of the balance sheet date of obligations incurred through that date and payable for obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

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Amount of additional cost recognized for award under share-based payment arrangement from occurrence of event accelerating recognition of cost.

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Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Discount rate from fair value on purchase date that participants pay for shares.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Amount of cash paid to settle liability for award under share-based payment arrangement.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Per share or unit weighted-average intrinsic value of award vested under share-based payment arrangement. Excludes share and unit options.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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.

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The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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Number of shares authorized for issuance under share-based payment arrangement.

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Number of grantees affected by modification of award under share-based payment arrangement.

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Number of shares issued under share-based payment arrangement.

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- Definition

Percentage of vesting of award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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Share-based Compensation - Narrative (Details)		1 Months Ended									2 Months Ended	12 Months Ended
Share-based Compensation - Narrative (Details)	Sep. 18, 2023 USD ($) employee $ / shares shares	Sep. 30, 2024 USD ($)	Aug. 31, 2024	Oct. 31, 2023	Aug. 31, 2023 shares	Dec. 31, 2022 USD ($) shares	Nov. 30, 2022 USD ($) employee	Sep. 30, 2022 USD ($)	Jun. 30, 2022 executive_award	Apr. 30, 2017	Jun. 30, 2022 employee	Mar. 31, 2025 USD ($) $ / shares shares	Mar. 31, 2024 USD ($) employee shares	Mar. 31, 2023 USD ($) $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional Paid in Capital												$ 2,922,000,000	$ 2,171,000,000
Non-current portion of accrued compensation and share-based compensation increase (decrease)												26,000,000	20,000,000
Staff costs: Share-based compensation cost (equity settled)												820,000,000	1,070,000,000	$ 326,000,000
Accrued compensation and benefits and share-based compensation increase (decrease)												140,000,000	298,000,000
IPO
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Sale of stock (in dollars per share) \| $ / shares	$ 51.00
2019 AEP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Accelerated share-based compensation														11,800,000
Staff costs: Share-based compensation cost (equity settled)													$ 217,200,000
Number of grantees affected by modification \| employee											435		5,251
2019 AEP \| Reclassification, Other Noncurrent Liabilities
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional Paid in Capital													$ 306,600,000
Non-current portion of accrued compensation and share-based compensation increase (decrease)													(306,600,000)
2019 EIP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share-based awards, liability paid												0	0	0
Staff costs: Share-based compensation cost (equity settled)	$ 4,100,000					$ 4,100,000		$ 4,500,000
Potential Fixed Monetary Amount						$ 20,000,000
2019 EIP \| Reclassification, Other Noncurrent Liabilities
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional Paid in Capital													5,700,000
Non-current portion of accrued compensation and share-based compensation increase (decrease)													(5,700,000)
2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Potential Fixed Monetary Amount														95,000,000
Accrued compensation and benefits and share-based compensation increase (decrease)														$ 32,000,000
Number of executive awards \| executive_award									2
Omnibus Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized share-based compensation												$ 989,800,000
Unrecognized share-based compensation, recognition period												1 year 2 months 12 days
Shares authorized (in shares) \| shares					20,500,000
Annual increase in shares authorized					2.00%
Restricted Stock Units (RSUs) \| 2019 AEP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting												100.00%
Aggregate nominal amount, limit												2.20%
Outstanding (in shares) \| shares														11,601,185
Share-based awards, liability paid													$ 18,200,000	$ 15,900,000
Fair value of awards														$ 16,200,000
Cash settlement, shares held by participant											50.00%
Restricted Stock Units (RSUs) \| 2019 EIP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Aggregate nominal amount, limit												30.00%
Outstanding (in shares) \| shares														192,999
Non-current portion of accrued compensation and share-based compensation increase (decrease)														$ 3,600,000
Shares cancelled (in shares) \| shares						355,463
Restricted Stock Units (RSUs) \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Aggregate nominal amount, limit									4.00%		4.00%
Accelerated share-based compensation	$ 17,700,000
Staff costs: Share-based compensation cost (equity settled)							$ 2,100,000
Number of grantees affected by modification \| employee	5,041						5,539
Unrecognized share-based compensation, recognition period												7 months 6 days
Restricted Stock Units (RSUs) \| Arm Non-Executive Directors RSU Award Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares) \| shares													31,806	13,340
Granted (in shares) \| shares													31,806	13,340
Restricted Stock Units - Cash Receipt \| 2019 AEP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Accelerated share-based compensation														$ 11,800,000
Restricted Stock Units - Retention Option \| 2019 AEP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Accelerated share-based compensation														2,200,000
Phantom Share Units (PSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares) \| shares												0	0
Share-based awards, liability paid													$ 900,000	1,500,000
Fair value of awards														$ 1,100,000
Vesting period										3 years
Vested (in shares) \| shares														(27,503)
Intrinsic value (in dollars per share) \| $ / shares														$ 38.84
Accrued compensation and benefits and share-based compensation increase (decrease)														$ 1,100,000
Launch Awards \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Potential Fixed Monetary Amount														80,000,000
Vesting period									3 years
Accrued compensation and benefits and share-based compensation increase (decrease)														23,000,000
Restricted Stock Units, Continuous Service \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period									3 years
Restricted Stock Units, Continuous Service \| Omnibus Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period				3 years
Restricted Stock Units, Time-Based \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period									3 years
Performance Shares, Continuous Service And Performance Conditions \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Service period									1 year
Performance Shares, Continuous Service And Performance Conditions \| Omnibus Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Service period				1 year
Performance Shares, Continuous Service And Performance Conditions \| Omnibus Incentive Plan \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting				0.00%
Performance Shares, Continuous Service And Performance Conditions \| Omnibus Incentive Plan \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting				200.00%
Annual Awards \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Potential Fixed Monetary Amount														15,000,000
Accrued compensation and benefits and share-based compensation increase (decrease)														$ 9,000,000
Annual Awards \| 2022 RSU Plan \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting									0.00%
Annual Awards \| 2022 RSU Plan \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting									200.00%
Executive Awards \| 2022 RSU Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Outstanding (in shares) \| shares												7,000,000	23,000,000
Staff costs: Share-based compensation cost (equity settled)	$ 9,800,000
Number of grantees affected by modification \| employee	14
Vested (in shares) \| shares												(16,000,000)
Shares issued (in shares) \| shares	1,875,202
Unrecognized share-based compensation												$ 264,700,000
Granted (in shares) \| shares												1,000,000
Granted (in dollars per share) \| $ / shares												$ 91.43
Executive Awards \| 2022 RSU Plan \| Reclassification, Other Noncurrent Liabilities
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional Paid in Capital	$ 20,200,000
Non-current portion of accrued compensation and share-based compensation increase (decrease)	(20,200,000)
Executive Awards \| 2022 RSU Plan \| Reclassification, Other Current Liabilities
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional Paid in Capital	9,100,000						$ 31,700,000
Accrued compensation and benefits and share-based compensation increase (decrease)	$ (9,100,000)						$ (31,700,000)
Performance Shares \| Omnibus Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period				3 years
Performance Shares, Time Based \| Omnibus Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period				3 years
Performance Shares, Continuous Service And Relative TSR
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period												3 years
Performance Shares, Continuous Service And Relative TSR \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting												0.00%
Performance Shares, Continuous Service And Relative TSR \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting												200.00%
Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized share-based compensation												$ 10,600,000
Duration of each purchase period under the ESPP												6 months
Share based compensation arrangement maximum employee subscription rate		10.00%
Maximum employee subscription amount		$ 25,000
Discount percent		15.00%
Granted (in dollars per share) \| $ / shares												$ 42.64
Shares issued in period (in shares) \| shares												0
Employee Stock \| Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Duration of each purchase period under the ESPP			6 months
Employee Stock \| Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Duration of each purchase period under the ESPP			24 months