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Cash and Cash Equivalents and Short-Term Investments (Details) £ in Millions, $ in Millions | Mar. 31, 2025 USD ($) | Mar. 31, 2025 GBP (£) | Dec. 31, 2024 USD ($) | Dec. 31, 2024 GBP (£)
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Cash, Cash Equivalents, and Short-Term Investments [Abstract] |  |  |  |
Cash and cash equivalents and short-term investments | $ 1,300 |  | $ 1,300 |
Restricted cash and investments | 138 |  | 123 |
Operating funds required to be held in U.K. | $ 85 | £ 66 | $ 79 | £ 63

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- Definition Short-Term Investments, Operating Funds Required To Be Held + References No definition available. + Details
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- Definition The current cash, cash equivalents and investments that are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against short-term borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. Includes current cash equivalents and investments that are similarly restricted as to withdrawal, usage or disposal. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 954 -SubTopic 210 -Name Accounting Standards Codification -Section 45 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477220/954-210-45-4 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 954 -SubTopic 210 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478600/954-210-50-2 + Details
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