Licensing, Acquisitions and Other Arrangements - Acquisition of ImmunoGen (Details) - USD ($) $ / shares in Units, $ in Millions		2 Months Ended	3 Months Ended
	Feb. 12, 2024	Mar. 31, 2024	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Business Acquisition
Amortization of intangible assets			$ 1,891	$ 1,948
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Goodwill		$ 33,426	33,426		$ 32,293
Pro Forma Information
Payments to Acquire Businesses, Net of Cash Acquired			9,199	0
ImmunoGen
Business Acquisition
Fair value step-up adjustment to inventories	$ 179
Weighted average useful life of acquired intangible assets		12 years
Net revenues attributable to ImmunoGen from acquisition date		$ 91
Operating earnings attributable to ImmunoGen from acquisition date		(404)
Inventory fair value step-up amortization		47
Amortization of intangible assets		21
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Cash and equivalents	591
Accounts receivable	171
Inventories	211
Prepaid expenses and other current assets	40
Property and equipment, net	7
Intangible Assets - Developed product rights	7,200
Business Combination Recognized Identifiable Assets Acquired And Liabilities License Agreements	125
Intangible assets - In-process research and development	1,280
Other noncurrent assets	273
Accounts payable and accrued liabilities	(312)
Current portion of long-term debt	(99)
Deferred income taxes	(899)
Other long-term liabilities	(47)
Total identifiable net assets	8,541
Goodwill	1,249
Total assets acquired and liabilities assumed	9,790
Pro Forma Information
Net revenues			12,365	12,275
Net earnings (loss)			$ 1,739	$ (413)
Cash consideration paid to ImmunoGen shareholders	9,800
Payments to Acquire Businesses, Net of Cash Acquired	9,200
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets	250
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized	349
Intangible Assets - Developed product rights	7,300
Intangible assets - In-process research and development	$ 1,300
Cash per share received by Cerevel Therapeutics shareholders (in dollars per share)	$ 31.26
ImmunoGen | Selling, general and administrative
Business Acquisition
Acquisition-related expenses		$ 59