Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 30, 2018
Document And Entity Information
Entity Registrant Name	AAON INC
Entity Central Index Key	0000824142
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2018
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		52,094,537