Business Acquisitions and Divestitures - Identified Assets Acquired and Liabilities Assumed (Oncology Research) (Details) - USD ($) $ in Millions	Oct. 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Identifiable assets acquired and liabilities assumed:
Goodwill		$ 10,132	$ 9,947	$ 9,451
U.S. Pharmaceutical
Identifiable assets acquired and liabilities assumed:
Goodwill		$ 4,123	$ 4,050	$ 3,923
SCRI Oncology, LLC | U.S. Pharmaceutical
Purchase consideration:
Cash	$ 166
Contribution of USOR	46
Total purchase consideration	212
Identifiable assets acquired and liabilities assumed:
Receivables	224
Property, plant, and equipment	22
Operating lease right-of-use assets	31
Intangible assets	177
Other non-current assets	6
Current liabilities	(42)
Long-term operating lease liabilities	(29)
Other non-current liabilities	(43)
Total identifiable net assets	346
Noncontrolling interest	(225)
Additional paid-in capital	(22)
Goodwill	113
Net assets acquired	$ 212