Cash and Cash Equivalents and Short-Term Investments (Details) £ in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2024 GBP (£)	Dec. 31, 2023 USD ($)	Dec. 31, 2023 GBP (£)
Cash, Cash Equivalents, and Short-Term Investments [Abstract]
Cash and cash equivalents and short-term investments	$ 6,400		$ 1,100
Increase in cash and cash equivalents and short term investments	5,300
Restricted cash and investments	112		120
Operating funds required to be held in U.K.	$ 70	£ 55	$ 80	£ 63