ALLIANCES - Financial Information Pertaining to Alliances (2seventy bio) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Alliance Statement [Line Items]
Total Revenues		$ 48,300	$ 45,006	$ 46,159
Cost of products sold	[1]	13,968	10,693	10,137
Net product sales
Alliance Statement [Line Items]
Total Revenues		46,778	43,778	44,671
Alliance revenues
Alliance Statement [Line Items]
Total Revenues		14,066	13,151	12,743
Cost of products sold		6,597	6,067	5,768
Alliance revenues | Net product sales
Alliance Statement [Line Items]
Total Revenues		13,587	12,543	12,001
2seventy bio | Alliance revenues
Alliance Statement [Line Items]
Cost of products sold		43	109	49
2seventy bio | Alliance revenues | Net product sales
Alliance Statement [Line Items]
Total Revenues		$ 242	$ 358	$ 297

[1] Excludes amortization of acquired intangible assets.