Collaborative Arrangements - CRISPR Therapeutics AG (Details)	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2015 USD ($) target
CRISPR Therapeutics
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Right to license, number of targets (up to) | target		6
Collaborative funding		$ 75,000,000.0
Collaborative arrangement development and regulatory potential milestone payments maximum		$ 420,000,000
CTX001 Co-Co Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative Arrangement Research and Development Expenses	$ 19,700,000