Collaborative Arrangements (Details)	3 Months Ended				6 Months Ended
	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) target	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)
CRISPR Therapeutics
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, right to exclusively license, number of targets | target			3
Collaborative arrangement, development and regulatory potential milestone payments maximum			$ 410,000,000.0
CTX001 Co-Co
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement research and development expenses	$ 9,800,000			$ 7,500,000	$ 19,000,000.0	$ 14,600,000
CRISPR DMD/DM1
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, development and regulatory potential milestone payments maximum					$ 800,000,000.0
Collaborative arrangement research and development expenses		$ 25,000,000.0