Financial Instruments and Fair Value Measurement (Details Textual) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Financial Instruments and Fair Value Measurement (Textual) [Abstract]
Security transfers between Levels 1 and 2	$ 0

Fair value assets level one and level two transfers amount.

No definition available.

Name:	clvs_FairValueAssetsLevelOneAndLevelTwoTransfersAmount
Namespace Prefix:	clvs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration