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Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Feb. 23, 2018
Jun. 30, 2017
Document And Entity Information      
Entity Registrant Name AAON INC    
Entity Central Index Key 0000824142    
Document Type 10-K    
Document Period End Date Dec. 31, 2017    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Is Entity a Well-known Seasoned Issuer? No    
Is Entity a Voluntary Filer? No    
Is Entity's Reporting Status Current? Yes    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   52,433,208  
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2017    
Entity Public Float     $ 1,502.1