Significant Contracts - Additional Information (Detail) € in Millions, shares in Millions, SFr in Millions						1 Months Ended			3 Months Ended	12 Months Ended
		Dec. 17, 2016 USD ($)	Feb. 12, 2016 USD ($)	Dec. 19, 2015 shares	Oct. 26, 2015 USD ($) Milestone	Mar. 31, 2016 USD ($)	Apr. 30, 2014 USD ($)	Apr. 30, 2014 CHF (SFr)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 22, 2016 USD ($)	Jan. 29, 2016 USD ($)	Nov. 30, 2014 USD ($)	Nov. 30, 2014 EUR (€)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense	[1]									$ 42,238,000	$ 12,573,000	$ 1,513,000
Research and development arrangement, description										The research collaboration will end on the earlier of the date on which Vertex has exercised six options to obtain exclusive/co-exclusive licenses with respect to a collaboration target, or the fourth anniversary of the effective date of the agreement. The research term may be extended as mutually agreed by the parties up to nine additional months to complete any research activities under the approved research plan that are incomplete on the fourth anniversary of the effective date.
Non-current deferred revenue										$ 77,646,000	75,090,000
Date of joint venture agreement										Dec. 19, 2015
Cash contribution										$ 100,000
Fair value allocation of arrangement consideration paid										91,200,000
Remaining license fee		$ 15,000,000
Other income (expense), net										78,512,000	16,000	(236,000)
Equity method investment										36,500,000
Unrealized equity method losses										(36,532,000)
Stock-based compensation expense										10,844,000	3,684,000	695,000
Licensing Agreements [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value										71,400,000
License and Patent Holder Consent [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value allocation of arrangement consideration paid										63,600,000
Future Research and Development Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value allocation of arrangement consideration paid										600,000
Bayer Convertible Loans [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Convertible Loan										35,000,000
Fair value of convertible loan										24,500,000
Fair value allocation of arrangement consideration paid										27,000,000
Debt instrument discount										8,000,000
Debt instrument face amount										$ 35,000,000
Loan agreement maturity date										Jan. 29, 2016
Bayer Convertible Loans [Member] | Series B Redeemable Convertible Preferred Shares [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value of convertible loan														$ 24,500,000
Loan agreement maturity date										Jan. 29, 2016
Bayer Global Investments B.V [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Value of shares to be purchased via option through private placement | shares				35.0
Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense										$ 1,200,000
Nonrefundable upfront payment received						$ 20,000,000
Aggregate consideration receivable										112,600,000
Revenue from collaboration agreement										1,200,000
Non-current deferred revenue										$ 500,000
Date of formation of joint venture entity										Feb. 12, 2016
Equity method investment, ownership percentage			50.00%			50.00%			50.00%	50.00%
Cash contribution			$ 100,000
Remaining license fees to be received from joint venture entity													$ 15,000,000
Royalty payments due to company from joint venture entity			0
Other payments due to company from joint venture entity			$ 0
Convertible Loan										$ 35,000,000
Cash contribution										100,000
Technology fee										34,900,000
Equity interest in the Joint Venture										36,400,000
Estimated revenue related to research and development services										6,300,000
Unrecognized equity method losses in excess of Company's interest										4,000,000
Stock-based compensation expense										200,000
Net loss of joint venture										(80,800,000)
Casebia Therapeutics LLP [Member] | Fair Value of CRISPR License Acquired [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense										77,400,000
Casebia Therapeutics LLP [Member] | Bayer Healthcare LLC [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense									$ 45,000,000
Equity method investment, ownership percentage			50.00%			50.00%			50.00%
Research and development funding term			5 years
Maximum [Member] | Casebia Therapeutics LLP [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from collaboration agreement			$ 35,000,000
Maximum [Member] | Casebia Therapeutics LLP [Member] | Bayer Healthcare LLC [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense			$ 300,000,000
Research and Development Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Fair value										6,300,000
Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense										$ 7,000,000	300,000
Clinical milestone payment payable					$ 10,000,000
Nonrefundable upfront payment received					75,000,000
Potential milestone receivable					420,000,000
Number of days to terminate the collaboration agreement										90 days
Notice period in the event of material breach of collaboration agreement										90 days
Number of days to terminate the product										270 days
Best estimate selling price for research and development services					26,700,000
Best estimated selling price for single collaboration					37,700,000
Best estimated selling price for collaboration agreement					188,500,000
Estimated selling price for collaboration agreement					50,000,000
Aggregate consideration receivable					151,700,000
Revenue from collaboration agreement										$ 4,000,000	200,000	0
Non-current deferred revenue										77,100,000	75,090,000
Vertex Pharmaceuticals Inc [Member] | Research and Development Services [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable					17,800,000
Patent Assignment Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense										33,000	100,000	0
Clinical milestone payment payable															$ 400,000	€ 0.3
Beta-Globin Collaboration [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Best estimated selling price for single collaboration					12,500,000
Non-Exclusive Research License and Exclusive License to Develop [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable					125,500,000
Non-Exclusive Research License and Co-Exclusive License to Develop [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable					8,400,000
Exclusive Option Agreement [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					10,000,000
Investigational New Drug Application ("IND") [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					10,000,000
Investigational New Drug Application ("IND") [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					$ 10,000,000
Clinical Development And Regulatory Milestone [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of developmental milestone events | Milestone					9
Clinical Development Milestones [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					$ 90,000,000
Regulatory Approval Milestone [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					235,000,000
Commercial Milestones [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					$ 75,000,000
Number of developmental milestone events | Milestone					2
Developmental Milestone Events [Member] | Vertex Pharmaceuticals Inc [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue recognition, milestone method, revenue recognized					$ 420,000,000
Commercial Milestone Event One [Member] | Vertex Pharmaceuticals Inc [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable					500,000,000
Commercial Milestone Event Two [Member] | Vertex Pharmaceuticals Inc [Member] | Minimum [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Aggregate consideration receivable					$ 1,000,000,000
CRISPR-Charpentier License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Upfront fees paid for license							$ 100,000	SFr 0.1
Annual payments for consulting agreement										0	0	0
Research and development expense										500,000	900,000	0
TRACR-Charpentier License Agreement [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development expense										$ 0	$ 100,000	$ 0

[1] Including the following amounts of research and development from a related party, see Note 16: