Collaborative Arrangements - CRISPR Therapeutics AG (Details)	3 Months Ended		12 Months Ended
	Dec. 31, 2019 USD ($) target	Sep. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
CRISPR Therapeutics
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative funding	$ 30,000,000.0
Right to license, number of targets (up to) | target	3
Collaborative arrangement development and regulatory potential milestone payments maximum	$ 410,000,000.0
CTX001 Co-Co Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement research and development expenses			$ 50,600,000	$ 30,100,000	$ 19,700,000
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
Collaborative arrangement, development and commercialization rights potential maximum milestone payments		$ 175,000,000.0