Discontinued operations - Significant Non-Cash Items and Capital Expenditures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Change in fair value of contingent consideration	$ 387	$ (6,468)	$ 2,747
Depreciation and amortization	4,900	5,100	4,100
Stock-based compensation expense	127,915	156,631	160,629
Investing activities:
Purchase of property, plant and equipment	(14,503)	(28,986)	(71,028)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300	0	0
Purchase of intangible assets	(8,500)	0	(5,224)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts    payable and accrued expenses	411	2,854	5,286
Right-of-use assets obtained in exchange for operating lease liabilities	202,221	19,414	23,939
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | 2seventy bio
Operating activities:
Change in fair value of contingent consideration	387	(6,468)	2,747
Depreciation and amortization	14,195	13,730	12,995
Stock-based compensation expense	29,175	34,036	29,545
Loss on fixed assets disposal	569	146	108
Loss on sale of Durham, North Carolina manufacturing facility	1,986	0	0
Investing activities:
Purchase of property, plant and equipment	(11,256)	(23,159)	(57,196)
Proceeds from sale of Durham, North Carolina manufacturing facility	110,300	0	0
Purchase of intangible assets	(8,500)	0	0
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts    payable and accrued expenses	778	2,039	3,064
Right-of-use assets obtained in exchange for operating lease liabilities	$ 151,520	$ 4,989	$ 9,745