CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Stock	Preferred Stock	Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Treasury Stock	Noncontrolling Interests in Consolidated Subsidiaries
Shares, issued, beginning balance at Dec. 31, 2014		245,811,180	0
Total equity, beginning balance at Dec. 31, 2014	$ 4,005,883	$ 2,458	$ 0	$ 1,541,583	$ (136,353)	$ 138,128	$ (953,701)	$ 3,413,768
Net income	379,195	0	0	0	0	244,977	0	134,218
Other comprehensive income (loss) (Note I)	(518)	0	0	0	9,111	0	0	(9,629)
Common stock issued	28,289	$ 0	0	(7,550)	0	0	35,839	0
Stock Issued During Period, Shares, Other		0
Common stock dividends	(509,197)	$ 0	0	(126,090)	0	(383,107)	0	0
Issuance of common units of ONEOK Partners	393,997	0	0	(34,446)	0	0	0	428,443
Distributions to noncontrolling interests	(535,825)	0	0	0	0	0	0	(535,825)
Other	4,512	$ 0	$ 0	4,947	0	2	0	(437)
Shares, issued, ending balance at Dec. 31, 2015		245,811,180	0
Total equity, ending balance at Dec. 31, 2015	3,766,336	$ 2,458	$ 0	1,378,444	(127,242)	0	(917,862)	3,430,538
Net income	743,499	0	0	0	0	352,039	0	391,460
Other comprehensive income (loss) (Note I)	(55,475)	0	0	0	(27,108)	0	0	(28,367)
Common stock issued	26,516	$ 0	0	2,331	0	0	24,185	0
Stock Issued During Period, Shares, Other		0
Common stock dividends	(517,601)	$ 0	0	(165,562)	0	(352,039)	0	0
Distributions to noncontrolling interests	(549,419)	0	0	0	0	0	0	(549,419)
Other	15,059	$ 0	$ 0	19,101	0	0	0	(4,042)
Shares, issued, ending balance at Dec. 31, 2016		245,811,180	0
Total equity, ending balance at Dec. 31, 2016	3,428,915	$ 2,458	$ 0	1,234,314	(154,350)	0	(893,677)	3,240,170
Cumulative effect adjustment for adoption of ASU 2016-09 at December 31, 2017	73,368	0	0	0	0	73,368	0	0
Net income	593,519	0	0	0	0	387,841	0	205,678
Other comprehensive income (loss) (Note I)	37,134	0	0	0	6,108	0	0	31,026
Common stock issued	473,586	$ 85	$ 0	456,537	0	0	16,964	0
Stock Issued During Period, Shares, Other		8,434,223	20,000
Preferred stock issued	20,000	$ 0	$ 0	20,000	0	0	0	0
Common stock dividends	(828,787)	0	0	(367,578)	0	(461,209)	0	0
Preferred stock dividends	(767)	0	0	(767)	0	0	0	0
Distributions to noncontrolling interests	(276,260)	$ 0	0	0	0	0	0	(276,260)
Stock Issued During Period, Shares, Acquisitions		168,920,831
Acquisition of ONEOK Partners' noncontrolling interests	2,146,462	$ 1,689	0	5,228,580	(40,288)	0	0	(3,043,519)
Other	18,182	$ 0	$ 0	17,792	0	0	0	390
Shares, issued, ending balance at Dec. 31, 2017		423,166,234	20,000
Total equity, ending balance at Dec. 31, 2017	$ 5,685,352	$ 4,232	$ 0	$ 6,588,878	$ (188,530)	$ 0	$ (876,713)	$ 157,485