Document and Entity Information
3 Months Ended
Mar. 31, 2014
Apr. 23, 2014
Document and Entity Information    
Entity Registrant Name CoreSite Realty Corp  
Entity Central Index Key 0001490892  
Document Type 10-Q  
Document Period End Date Mar. 31, 2014  
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   21,626,100
Document Fiscal Year Focus 2014  
Document Fiscal Period Focus Q1