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, 2015		245,811,180	0
Total equity, beginning 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 H)	(55,475)	$ 0	0	0	(27,108)	0	0	(28,367)
Stock Issued During Period, Shares, Other		0
Stock Issued During Period, Value, Other	26,516	$ 0	0	2,331	0	0	24,185	0
Common stock dividends (Note G)	(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 ASUs	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 H)	37,134	0	0	0	6,108	0	0	31,026
Preferred stock issued	20,000	0	0	20,000	0	0	0	0
Preferred stock dividends (Note G)	(767)	$ 0	$ 0	(767)	0	0	0	0
Stock Issued During Period, Shares, Other		8,434,223	20,000
Stock Issued During Period, Value, Other	473,586	$ 85	$ 0	456,537	0	0	16,964	0
Common stock dividends (Note G)	(828,787)	0	0	(367,578)	0	(461,209)	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 (Note A)	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
Cumulative effect adjustment for adoption of ASUs	1,719	0	0	0	(38,101)	39,803	0	17
Net income	1,155,032	0	0	0	0	1,151,703	0	3,329
Other comprehensive income (loss) (Note H)	38,392	0	0	0	38,392	0	0	0
Preferred stock dividends (Note G)	(1,100)	$ 0	0	0	0	(1,100)	0	0
Stock Issued During Period, Shares, Other		21,850,000
Stock Issued During Period, Value, Other	1,208,446	$ 218	0	1,183,321	0	0	24,907	0
Common stock dividends (Note G)	(1,335,211)	0	0	(144,805)	0	(1,190,406)	0	0
Distributions to noncontrolling interests	(3,500)	0	0	0	0	0	0	(3,500)
Contributions from noncontrolling interests	16,449	$ 0	0	0	0	0	0	16,449
Stock Issued During Period, Shares, Acquisitions		0
Acquisition of noncontrolling interests (Note G)	(195,000)	$ 0	0	(21,220)	0	0	0	(173,780)
Other	8,964	$ 0	$ 0	8,964	0	0	0	0
Shares, issued, ending balance at Dec. 31, 2018		445,016,234	20,000
Total equity, ending balance at Dec. 31, 2018	$ 6,579,543	$ 4,450	$ 0	$ 7,615,138	$ (188,239)	$ 0	$ (851,806)	$ 0