Related Party Transactions (Details)		12 Months Ended
Mar. 31, 2013 item	Dec. 31, 2012 Chief executive officer Stock option	Dec. 31, 2012 Chief executive officer Restricted stock units
Related Party Transactions
Number of principal stockholders for which chief executive officer serves as a general partner	1
Related Party Transactions
Granted (in shares)		339,313	192,308

Represents the number of principal stockholders of the entity for which the entity's chief executive officer serves as a general partner.

No definition available.

Name:	ovas_NumberOfPrincipalStockholdersForWhichChiefExecutiveOfficerServesAsAGeneralPartner
Namespace Prefix:	ovas_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant