ALLIANCES - Financial Information Pertaining to Alliances (2seventy bio) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total Revenues		$ 46,385	$ 42,518	$ 26,145
Cost of products sold	[1]	9,940	11,773	8,078
Net product sales
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total Revenues		45,055	41,321	25,174
Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total Revenues		11,556	9,979	10,541
Cost of products sold		5,227	4,485	4,169
Collaborative Arrangement | Net product sales
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total Revenues		10,840	9,364	$ 9,944
2seventy bio | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment related to the collaboration agreement			$ 200
2seventy bio | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of products sold		42
2seventy bio | Collaborative Arrangement | Net product sales
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total Revenues		$ 158

[1] Excludes amortization of acquired intangible assets.