Selected Quarterly Financial Data (Unaudited) - Additional Information (Detail) $ in Millions	3 Months Ended
Dec. 31, 2016 USD ($)
Quarterly Financial Information Disclosure [Abstract]
Net Income attributable to Participating securities excluded from numerator for calculating basic net income per share	$ 3.1
Net Income attributable to participating securities excluded from numerator for calculating diluted net income per share	$ 3.1

Net Income loss attributable to participating securities excluded from numerator for calculating diluted net income (loss) per share.

No definition available.

Name:	crsp_NetIncomeLossAttributableToParticipatingSecuritiesExcludedFromNumeratorForCalculatingDilutedNetIncomeLossPerShare
Namespace Prefix:	crsp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration