Business Acquisitions and Divestitures - Identified Assets Acquired and Liabilities Assumed (Rx Savings Solutions) (Details) - USD ($) $ in Millions	Nov. 01, 2022	Oct. 31, 2022	Dec. 31, 2023	Mar. 31, 2023
Identifiable assets acquired and liabilities assumed:
Goodwill			$ 9,973	$ 9,947
U.S. Pharmaceutical
Identifiable assets acquired and liabilities assumed:
Goodwill			$ 4,043	$ 4,050
Rx Savings Solutions, LLC | RxTs Segment
Purchase consideration:
Cash	$ 600
Contingent consideration	92
Total purchase consideration	692
Identifiable assets acquired and liabilities assumed:
Current assets	5
Intangible assets	229
Other non-current assets	3
Current liabilities	(8)
Total identifiable net assets	229
Goodwill	463
Net assets acquired	$ 692
SCRI Oncology, LLC | U.S. Pharmaceutical
Purchase consideration:
Cash		$ 166
Total purchase consideration		212
Identifiable assets acquired and liabilities assumed:
Intangible assets		177
Other non-current assets		6
Current liabilities		(42)
Total identifiable net assets		346
Goodwill		113
Net assets acquired		$ 212