Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.10.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2018
Jan. 31, 2019
Jun. 29, 2018
Document and Entity Information [Abstract]      
Entity Registrant Name STAMPS.COM INC    
Entity Central Index Key 0001082923    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 4,415,776,705
Entity Common Stock, Shares Outstanding   17,527,387  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false