Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Claim	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Contingencies And Commitments [Line Items]
Cost sharing expensed relating to patent maintenance, defense and prosecution, incurred	$ 2.9	$ 2.4	$ 1.2
Cost sharing expensed relating to patent maintenance, defense and prosecution, accrued	$ 1.5	$ 1.9
Patent Applications Co-owned by CVC Group [Member]
Contingencies And Commitments [Line Items]
Number of patent and patent applications pending | Claim	14
Patents and Patent Application Owned by Broad [Member]
Contingencies And Commitments [Line Items]
Number of patent and patent applications pending | Claim	13
2015 Collaboration Agreement [Member] | Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member]
Contingencies And Commitments [Line Items]
Milestone payment receivable	$ 395.0