Accounts Receivable, Net - Allowances and Factoring Facility (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jul. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	May 31, 2024
Receivables [Abstract]
Allowance for receivables, current		$ 5,000,000,000.0	$ 3,700,000,000
Pharmaceutical manufacturers receivables allowance		4,300,000,000	3,100,000,000
Noninsurance customer receivables allowance		388,000,000	386,000,000
Allowance for current expected credit losses on accounts receivable		$ 84,000,000	90,000,000
Initial term, uncommitted factoring facility (in years)	2 years
Automatic renewal term, uncommitted factoring facility (in years)		1 year
Total capacity, uncommitted factoring facility	$ 1,000,000,000.0	$ 1,500,000,000		$ 1,500,000,000
Accounts receivable sold, uncommitted factoring facility		5,500,000,000	2,100,000,000
Accounts receivable sold that remain outstanding, uncommitted factoring facility		0	0
Accounts receivable received but not remitted, uncommitted factoring facility		$ 1,000,000,000.0	$ 515,000,000