EARNINGS PER SHARE EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Basic EPS from Continuing Operations [Abstract]
Income from continuing operations attributable to ONEOK available for common stock									$ 387,074	$ 354,090	$ 251,058
Shares									297,477	211,128	210,208
Basic	$ 0.16	$ 0.43	$ 0.34	$ 0.41	$ 0.43	$ 0.44	$ 0.41	$ 0.40	$ 1.30	$ 1.68	$ 1.19
Diluted EPS from Continuing Operations [Abstract]
Effect of options and other dilutive securities									$ 0	$ 0	$ 0
Effect of options and other dilutive securities, number of shares, shares									2,303	1,255	333
Income from continuing operations attributable to ONEOK available for common stock and common stock equivalents									$ 387,074	$ 354,090	$ 251,058
Shares									299,780	212,383	210,541
Diluted	$ 0.16	$ 0.43	$ 0.33	$ 0.41	$ 0.43	$ 0.43	$ 0.40	$ 0.40	$ 1.29	$ 1.67	$ 1.19