Collaborative Arrangements and Acquisitions - CRISPR Therapeutics AG (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2015
CRISPR Therapeutics
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement, up-front payment						$ 75.0
Collaborative arrangement, development and regulatory potential milestone payments maximum						$ 420.0
CTX001 Co-Co
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement research and development expenses		$ 7.5	$ 5.2	$ 14.6	$ 8.9
Subsequent Event | CRISPR Therapeutics
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative arrangement, up-front payment	$ 175.0
Collaborative arrangement, development and regulatory potential milestone payments maximum	$ 825.0