Discontinued operations - Significant Non-Cash Items and Capital Expenditures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating activities:
Change in fair value of contingent consideration	$ 0	$ 369
Stock-based compensation expense	12,390	42,527
Investing activities:
Purchase of property, plant and equipment	(857)	(7,626)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses	$ 2,134	2,238
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | 2seventy bio
Operating activities:
Change in fair value of contingent consideration		369
Depreciation and amortization		3,800
Stock-based compensation expense		11,181
Investing activities:
Purchase of property, plant and equipment		(6,173)
Supplemental cash flow disclosures:
Purchases of property, plant and equipment included in accounts payable and accrued expenses		$ 1,954