Royalty and other revenue - Narrative (Detail) - Royalty and other revenue - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
License And Royalty Revenue [Line Items]
Milestone payment	$ 6,200	$ 21,100	$ 8,200	$ 6,220	$ 21,076	$ 8,205
Juno Therapeutics | Bluebird Bio
License And Royalty Revenue [Line Items]
Milestone payment	$ 2,500