Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 24, 2020	Jun. 30, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	0-18953
Entity Registrant Name	AAON, INC.
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	87-0448736
Entity Address, Address Line One	2425 South Yukon Ave.,
Entity Address, City or Town	Tulsa,
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74107
City Area Code	918
Local Phone Number	583-2266
Title of 12(b) Security	Common Stock
Trading Symbol	AAON
Security Exchange Name	NASDAQ
Is Entity a Well-known Seasoned Issuer?	No
Is Entity a Voluntary Filer?	No
Is Entity's Reporting Status Current?	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 2,035.2
Entity Common Stock, Shares Outstanding		52,092,212
Documents Incorporated by Reference	Portions of registrant’s definitive Proxy Statement to be filed in connection with the Annual Meeting of Stockholders to be held May 12, 2020, are incorporated into Part III.
Entity Central Index Key	0000824142
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false