Third-Party Arrangements - Schedule of Amount Due (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Due from Merck in Accounts receivable	$ 1,484	$ 1,358
Due to Merck in Accounts payable	1,074	1,153
Related Party
Related Party Transaction [Line Items]
Due from Merck in Accounts receivable	162	148
Due to Merck in Accounts payable	$ 401	$ 362