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Significant Contracts - Additional Information (Detail) |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
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Dec. 13, 2019 USD ($) Product | Oct. 26, 2015 USD ($) | Oct. 31, 2019 License | Sep. 30, 2020 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Sep. 30, 2020 USD ($) Option | Sep. 30, 2019 USD ($) | Dec. 31, 2016 USD ($) | Apr. 30, 2020 USD ($) | Dec. 12, 2019
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-current deferred revenue |  |  |  |  | $ 11,776,000 |  |  | $ 11,776,000 |  |  |  | $ 11,776,000 |  |  |  |
Collaboration revenue | [1] |  |  |  | 148,000 |  |  |  | $ 211,928,000 |  |  | 349,000 | $ 212,574,000 |  |  |
Current deferred revenue |  |  |  |  | 610,000 |  |  | 960,000 |  |  |  | 610,000 |  |  |  |
Research and development expense | [2] |  |  |  | 71,008,000 |  |  |  | 57,246,000 |  |  | $ 184,581,000 | 130,601,000 |  |  |
Date of joint venture agreement |  |  |  |  |  |  |  |  |  |  |  | Dec. 19, 2015 |  |  |  |
Operating expenses |  |  |  |  | 92,547,000 |  |  |  | 72,765,000 |  |  | $ 247,023,000 | 176,817,000 |  |  |
Equity method investment |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 36,500,000 |  |
Unrealized equity method losses |  |  |  |  |  |  |  |  | 3,430,000 |  |  |  | 5,467,000 | $ 36,500,000 |  |
Net loss of joint venture |  |  |  |  | (92,439,000) | $ (79,656,000) | $ (69,731,000) |  | 138,423,000 | $ (53,699,000) | $ (48,408,000) | (241,826,000) | 36,316,000 |  |  |
Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  |  |  |  |  | 100,000 |  |  |  | 700,000 |  |  |
Equity method investment, ownership percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%
Unrealized equity method losses |  |  |  |  |  |  |  |  | 3,300,000 |  |  |  | 5,500,000 |  |  |
Net loss of joint venture |  |  |  |  |  |  |  |  | 22,600,000 |  |  |  | 54,900,000 |  |  |
Unrecognized equity method losses in excess of Company's interest |  |  |  |  |  |  |  |  |  |  |  |  | 70,100,000 |  |  |
Business combination, consideration transferred |  |  |  |  |  |  |  |  |  |  |  | 41,000,000.0 |  |  |  |
Net assets acquired |  |  |  |  | $ 16,000,000.0 |  |  |  |  |  |  | 16,000,000.0 |  |  |  |
Fair value of controlling interest obtained |  |  |  |  |  |  |  |  |  |  |  | $ 32,000,000.0 |  |  |  |
Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Date of formation of joint venture entity |  |  |  |  |  |  |  |  |  |  |  | Feb. 12, 2016 |  |  |  |
Equity method investment, ownership percentage |  |  |  |  | 50.00% |  |  |  |  |  |  | 50.00% |  |  |  |
License and Service [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Collaboration revenue |  |  |  |  |  |  |  |  | 100,000 |  |  |  | 500,000 |  |  |
Non-Exclusive Research License [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Transaction price allocated to remaining performance obligations |  |  | $ 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Non-Exclusive Research License [Member] | Valuation, Market Approach |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for collaboration agreement |  |  | 1,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |
Retirement Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of partnership interests |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Partnership outstanding exchange amount |  | $ 22,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating expenses |  | $ 6,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
2019 Option Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and development expense |  |  |  |  | $ 4,400,000 |  |  |  |  |  |  | $ 8,600,000 |  |  |  |
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of options exercised under agreement | Option |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |
Equity method investment, ownership percentage |  |  |  |  | 50.00% |  |  |  |  |  |  | 50.00% |  |  |  |
Business combination, consideration transferred |  |  |  |  |  |  |  |  |  |  |  | $ 25,000,000.0 |  |  |  |
Payment to acquire business |  |  |  |  |  |  |  |  |  |  |  | 16,000,000.0 |  |  |  |
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] | Research And Development Services |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of obligations |  |  |  |  | $ 20,200,000 |  |  |  |  |  |  | 20,200,000 |  |  |  |
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] | Future Delivery of up to Two Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fair value of obligations |  |  |  |  | 4,800,000 |  |  |  |  |  |  | 4,800,000 |  |  |  |
2019 Option Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of products | Product |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Non-refundable one-time option payment |  | $ 20,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
2019 Option Agreement [Member] | Research and Development [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business combination, consideration transferred |  |  |  |  |  |  |  |  |  |  |  | 20,200,000 |  |  |  |
2019 Option Agreement [Member] | Certain Options [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Business combination, consideration transferred |  |  |  |  |  |  |  |  |  |  |  | 4,800,000 |  |  |  |
Co-commercialization Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of research and development costs |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage sharing of profit (loss) from sale of product |  | 50.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
2019 Casebia Agreement [Member] | Other Current Liabilities [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research obligation |  |  |  |  | 11,600,000 |  |  |  |  |  |  | 11,600,000 |  |  |  |
2019 Casebia Agreement [Member] | Other Long-term Liabilities [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research obligation |  |  |  |  | 4,800,000 |  |  |  |  |  |  | 4,800,000 |  |  |  |
2019 Casebia Agreement [Member] | Casebia Therapeutics Limited Liability Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity method investment |  |  |  |  | 0 |  |  |  |  |  |  | 0 |  |  |  |
Fair value of assets and liabilities |  |  |  |  | 16,000,000.0 |  |  |  |  |  |  | 16,000,000.0 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nonrefundable upfront payment received |  |  | 75,000,000.0 |  |  |  |  |  |  |  |  | 175,000,000.0 |  |  |  |
Milestone payment receivable |  |  |  |  | 410,000,000.0 |  |  |  |  |  |  | 410,000,000.0 |  |  |  |
Transaction price |  |  |  |  |  |  |  |  |  |  |  | 268,600,000 |  |  |  |
Non-current deferred revenue |  |  |  |  | 11,800,000 |  |  | 11,800,000 |  |  |  | 11,800,000 |  |  |  |
Non-cash consideration received |  |  |  |  |  |  |  |  |  |  |  | 10,000,000.0 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 12,000,000.0 |  |  |  |  |  |  | 12,000,000.0 |  |  |  |
Collaboration revenue |  |  |  |  | 0 |  |  |  | 211,900,000 |  |  | 0 | 212,100,000 |  |  |
Current deferred revenue |  |  |  |  | 600,000 |  |  | 900,000 |  |  |  | 600,000 |  |  |  |
Maximum potential future payments |  |  |  |  |  |  |  |  |  |  |  | 800,000,000.0 |  |  |  |
Contract asset |  |  |  |  | 25,000,000.0 |  |  |  |  |  |  | 25,000,000.0 |  |  |  |
Research and development expense |  |  |  |  | 12,500,000 |  |  |  | 7,500,000 |  |  | 31,500,000 | 21,300,000 |  |  |
Reimbursements from research and license agreements |  |  |  |  | 6,800,000 |  |  |  | $ 3,800,000 |  |  | 17,800,000 | $ 11,800,000 |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Research and Development [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable consideration received |  |  | 19,300,000 |  |  |  |  |  |  |  |  | 25,000,000.0 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Milestone payment receivable |  |  |  |  | 420,000,000.0 |  |  |  |  |  |  | 420,000,000.0 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 46,700,000 |  |  |  |  |  |  | 46,700,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 R&D Services [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 1,700,000 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 1,100,000 |  |  |  |  |  |  | 1,100,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 R&D Services [Member] | Research and Development [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Variable consideration received |  |  |  |  |  |  |  |  |  |  |  | 800,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DMD License [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 224,600,000 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 151,100,000 |  |  |  |  |  |  | 151,100,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | DM1 License [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 76,200,000 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 51,300,000 |  |  |  |  |  |  | 51,300,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Specified Target Option Material Right |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 17,500,000 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | 11,800,000 |  |  |  |  |  |  | 11,800,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 25,000,000.0 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 22,200,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Collaboration Target Options Material Rights Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | 22,200,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Joint Development Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Up-front payment received |  |  | 7,000,000.0 |  |  |  |  |  |  |  |  | $ 7,000,000.0 |  |  |  |
Agreement description |  |  |  |  |  |  |  |  |  |  |  | In connection with the JDA, the Company received a $7.0 million up-front payment from Vertex and subsequently received a one-time low seven-digit milestone payment upon the dosing of the second patient in a clinical trial with the initial product candidate. |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | Exercise of Exclusive Option [Member] | Collaboration Target Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Milestone payment receivable |  |  |  |  | 10,000,000 |  |  |  |  |  |  | $ 10,000,000 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2019 Collaboration Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nonrefundable upfront payment received |  |  |  |  |  |  |  |  |  |  |  | 175,000,000.0 |  |  |  |
Maximum potential payments |  |  |  |  | 825,000,000.0 |  |  |  |  |  |  | $ 825,000,000.0 |  |  |  |
Percentage of exchange payment of research and development costs |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |
Collaborative arrangement, license rights reacquired by waiving payment owed |  |  |  |  |  |  |  |  |  |  |  | $ 10,000,000.0 |  |  |  |
Non-cash consideration expensed upon execution of collaborative agreement |  |  |  |  |  |  |  |  |  |  |  | 10,000,000.0 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2015 Collaboration Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Milestone payment receivable |  |  |  |  | 395,000,000.0 |  |  |  |  |  |  | $ 395,000,000.0 |  |  |  |
Percentage of exchange payment of research and development costs |  |  |  |  |  |  |  |  |  |  |  | 50.00% |  |  |  |
Number of options would not be exercised under agreement | Option |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |
Number of remaining options under agreement | Option |  |  |  |  |  |  |  |  |  |  |  | 4 |  |  |  |
Non-current deferred revenue |  |  |  |  | 57,800,000 |  |  |  |  |  |  | $ 57,800,000 |  |  |  |
Number of options exercised under agreement | Option |  |  |  |  |  |  |  |  |  |  |  | 4 |  |  |  |
Vertex Pharmaceuticals Incorporated and Certain of its Subsidiaries [Member] | 2015 Collaboration Agreement [Member] | Collaborative Arrangement Material Rights Fourth Exclusive License |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  |  |  |  |  |  |  |  |  |  | $ 10,000,000.0 |  |  |  |
Transaction price allocated to remaining performance obligations |  |  |  |  | $ 6,700,000 |  |  |  |  |  |  | $ 6,700,000 |  |  |  |
Vertex Pharmaceuticals Inc [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 19,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Transaction price allocated to remaining performance obligations |  |  | 19,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for collaboration agreement |  |  | 118,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Collaboration Target Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Transaction price allocated to remaining performance obligations |  |  | 57,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Collaboration Target Options Material Rights One [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 45,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Collaboration Target Options Material Rights Two [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 38,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Collaboration Target Options Material Rights Three [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 17,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Rights Four [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 17,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | 2019 Collaboration Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Milestone payment receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 25,000,000.0 |
Vertex Pharmaceuticals Inc [Member] | 2015 Collaboration Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate amount in option exercise payments received |  |  |  |  |  |  |  | $ 30,000,000.0 |  |  |  |  |  |  |  |
Number of exclusive license targets | License |  |  |  | 3 |  |  |  |  |  |  |  |  |  |  |  |
Vertex Pharmaceuticals Inc [Member] | Beta Globin |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Research and Development Arrangement, Contract to Perform for Others [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated standalone selling price for single collaboration |  |  | 48,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Transaction price allocated to remaining performance obligations |  |  | $ 23,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Including the following revenue from a related party, see Notes 7 & 12
[2] | Including the following research and development expense with a related party, see Notes 7 & 12

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