XML 16 R26.htm IDEA: XBRL DOCUMENT  v2.3.0.11
Document and Entity Information
6 Months Ended
Jun. 30, 2011
Aug. 08, 2011
Document and Entity Information    
Entity Registrant Name COWEN GROUP, INC.  
Entity Central Index Key 0001466538  
Document Type 10-Q  
Document Period End Date Jun. 30, 2011
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   116,291,426
Document Fiscal Year Focus 2011  
Document Fiscal Period Focus Q2