Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 19, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-13643
Entity Registrant Name	ONEOK, Inc.
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1520922
Entity Address, Address Line One	100 West Fifth Street,
Entity Address, City or Town	Tulsa,
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74103
City Area Code	918
Local Phone Number	588-7000
Title of 12(b) Security	Common stock, par value of $0.01
Trading Symbol	OKE
Security Exchange Name	NYSE
Entity Current Reporting Status	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 Common Stock, Shares Outstanding		444,397,414
Entity Central Index Key	0001039684
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false