QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total revenues	$ 3,792,158	$ 2,906,366	$ 2,725,772	$ 2,749,611	$ 2,654,461	$ 2,357,907	$ 2,134,107	$ 1,774,459	$ 12,173,907	$ 8,920,934	$ 7,763,206
Income from continuing operations					194,761	194,792	180,086	175,911	593,519	745,550	385,276
Income (loss) from discontinued operations, net of tax					(296)	(576)	(227)	(952)	0	(2,051)	(6,081)
Net income	64,812	166,531	175,991	186,185	194,465	194,216	179,859	174,959	593,519	743,499	379,195
Net income attributable to ONEOK	63,045	165,742	71,693	87,361	$ 90,505	$ 92,144	$ 85,944	$ 83,446	387,841	352,039	244,977
Net Income Available to Common Stockholders	$ 62,771	$ 165,466	$ 71,476	$ 87,361					$ 387,074	$ 352,039	$ 244,977
Earnings Per Share [Abstract]
Basic	$ 0.16	$ 0.43	$ 0.34	$ 0.41	$ 0.43	$ 0.44	$ 0.41	$ 0.40	$ 1.30	$ 1.68	$ 1.19
Diluted	$ 0.16	$ 0.43	$ 0.33	$ 0.41	$ 0.43	$ 0.43	$ 0.40	$ 0.40	$ 1.29	$ 1.67	$ 1.19
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount									$ 141,283	$ 43	$ 928
Asset Impairment Charges									20,240	0	264,256
Noncash Contribution Expense									12,600	$ 0	$ 0
Business Combination, Acquisition Related Costs									30,000
Series E Preferred Stock [Member]
Earnings Per Share [Abstract]
Noncash Contribution Expense									$ 20,000