DISCONTINUED OPERATIONS (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill, Impairment Loss									$ 0	$ 0	$ 10,255,000
Disposal Group, Including Discontinued Operation, Assets, Current	16,717,000				747,872,000				16,717,000	747,872,000
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents					3,748,000					3,748,000
Disposal Group, Including Discontinued Operation, Other Assets, Current					59,804,000					59,804,000
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment					3,065,551,000					3,065,551,000
Disposal Group, Including Discontinued Operation, Goodwill					157,953,000					157,953,000
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent	20,020,000				402,546,000				20,020,000	402,546,000
Disposal Group, Including Discontinued Operation, Assets	36,737,000				4,373,922,000				36,737,000	4,373,922,000
Disposal Group, Including Discontinued Operation, Liabilities, Current	44,901,000				455,688,000				44,901,000	455,688,000
Accumulated Charges Attributable To Exit Activities	73,800,000				122,000,000				73,800,000	122,000,000	0
Assets	15,304,560,000				17,741,481,000				15,304,560,000	17,741,481,000	15,900,973,000
Proceeds from Divestiture of Businesses and Interests in Affiliates											32,900,000
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax									0	0	13,517,000
Gain on sale of business, tax impact											8,300,000
Business Exit Costs									1,700,000	138,600,000
Effect on Future Cash Flows, Amount									45,000,000
Disposal Group, Including Discontinued Operation, Operating Expenses Related to Separation									23,000,000	9,400,000
Stockholders' Equity Note, Spinoff Transaction									(1,749,588,000)
Proceeds from Divestiture of Businesses, Net of Cash Divested											22,500,000
Description and timing of discontinued operations											On February 1, 2012, we sold ONEOK Energy Marketing Company, our Natural Gas Distribution segment’s retail natural gas marketing business, to Constellation Energy Group, Inc. for $22.5 million plus working capital.
Revenues									640,653,000	3,071,581,000	2,825,419,000
Cost of sales and fuel									555,541,000	2,431,565,000	2,116,734,000
Net margin									85,112,000	640,016,000	708,685,000
Operating costs									65,898,000	448,867,000	417,661,000
Operating income									7,860,000	46,115,000	150,251,000
Settlements of business exit costs									(51,800,000)	(17,700,000)
Accretion Expense									1,900,000	1,100,000
Disposal Group, Including Discontinued Operation, Depreciation and Amortization									11,354,000	145,034,000	130,518,000
Disposal Group, Including Discontinued Operation, Other Income									(895,000)	2,619,000	1,586,000
Disposal Group, Including Discontinued Operation, Interest Expense									(5,005,000)	(63,561,000)	(64,668,000)
Discontinued Operation, Tax Effect of Discontinued Operation									(7,567,000)	2,698,000	(34,904,000)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	799,000	(171,000)	(8,009,000)	1,774,000	17,077,000	(10,126,000)	(74,282,000)	55,202,000	(5,607,000)	(12,129,000)	52,265,000
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net					455,529,000					455,529,000
Disposal Group, Including Discontinued Operation, Inventory					228,791,000					228,791,000
Disposal Group, Including Discontinued Operation, Current Maturities of Long-Term Debt					6,000					6,000
Disposal Group, Including Discontinued Operation, Accounts Payable					246,072,000					246,072,000
Disposal Group, Including Discontinued Operation, Other Liabilities, Current					209,610,000					209,610,000
Disposal Group, Including Discontinued Operation, Long Term Debt Excluding Current Portion					1,318,000					1,318,000
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities, Noncurrent					791,700,000					791,700,000
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent	36,424,000				255,212,000				36,424,000	255,212,000
Disposal Group, Including Discontinued Operation, Liabilities	81,325,000				1,503,918,000				81,325,000	1,503,918,000
Natural Gas Distribution [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents					3,535,000					3,535,000
Disposal Group, Including Discontinued Operation, Other Assets, Current					30,328,000					30,328,000
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment					3,065,272,000					3,065,272,000
Disposal Group, Including Discontinued Operation, Goodwill					157,953,000					157,953,000
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent					402,161,000					402,161,000
Disposal Group, Including Discontinued Operation, Assets					4,193,591,000					4,193,591,000
Assets												4,300,000,000
Liabilities												2,600,000,000
Accounts Receivable, Related Parties, Current					130,000,000					130,000,000
Notes Receivable, Related Parties, Noncurrent					1,000,000,000					1,000,000,000
Stockholders' Equity Note, Spinoff Transaction				1,700,000,000
Description and timing of discontinued operations									On January 31, 2014, we completed the separation of ONE Gas. ONE Gas consists of our former natural gas distribution business that includes Kansas Gas Service, Oklahoma Natural Gas and Texas Gas Service. ONEOK shareholders of record at the close of business on January 21, 2014, retained their shares of ONEOK stock and received one share of ONE Gas stock for every four shares of ONEOK stock owned in a transaction that was tax-free to ONEOK and its shareholders. ONE Gas shares were distributed following the close of business on January 31, 2014.
Revenues									287,249,000	1,689,945,000	1,404,248,000
Cost of sales and fuel									190,893,000	876,944,000	646,220,000
Net margin									96,356,000	813,001,000	758,028,000
Operating costs									60,847,000	436,281,000	400,247,000
Operating income									24,474,000	231,962,000	227,623,000
Disposal Group, Including Discontinued Operation, Depreciation and Amortization									11,035,000	144,758,000	130,158,000
Disposal Group, Including Discontinued Operations, Goodwill Impairment											0
Disposal Group, Including Discontinued Operation, Other Income									(888,000)	2,484,000	1,439,000
Disposal Group, Including Discontinued Operation, Interest Expense									(4,592,000)	(61,366,000)	(60,794,000)
Discontinued Operation, Tax Effect of Discontinued Operation									(16,415,000)	(64,307,000)	(63,647,000)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									2,579,000	108,773,000	104,621,000
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net					368,214,000					368,214,000
Disposal Group, Including Discontinued Operation, Inventory					166,128,000					166,128,000
Disposal Group, Including Discontinued Operation, Current Maturities of Long-Term Debt					6,000					6,000
Disposal Group, Including Discontinued Operation, Accounts Payable					168,785,000					168,785,000
Disposal Group, Including Discontinued Operation, Other Liabilities, Current					168,964,000					168,964,000
Disposal Group, Including Discontinued Operation, Long Term Debt Excluding Current Portion					1,318,000					1,318,000
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities, Noncurrent					826,921,000					826,921,000
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent					184,214,000					184,214,000
Disposal Group, Including Discontinued Operation, Liabilities					1,350,208,000					1,350,208,000
Energy Services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents					213,000					213,000
Disposal Group, Including Discontinued Operation, Other Assets, Current					29,476,000					29,476,000
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment					279,000					279,000
Disposal Group, Including Discontinued Operation, Goodwill					0					0
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent					385,000					385,000
Disposal Group, Including Discontinued Operation, Assets					180,331,000					180,331,000
Accounts Receivable, Related Parties, Current					25,100,000					25,100,000
Notes Receivable, Related Parties, Noncurrent					21,400,000					21,400,000
Description and timing of discontinued operations									On March 31, 2014, we completed the accelerated wind down of our energy services business. We executed agreements in 2013 to release a significant portion of our nonaffiliated natural gas transportation and storage contracts to third parties between July 1 and December 31, 2013.
Revenues									353,404,000	1,381,636,000	1,421,171,000
Cost of sales and fuel									364,648,000	1,554,621,000	1,470,514,000
Net margin									(11,244,000)	(172,985,000)	(49,343,000)
Operating costs									5,051,000	12,586,000	17,414,000
Operating income									(16,614,000)	(185,847,000)	(77,372,000)
Disposal Group, Including Discontinued Operation, Depreciation and Amortization									319,000	276,000	360,000
Disposal Group, Including Discontinued Operations, Goodwill Impairment											10,255,000
Disposal Group, Including Discontinued Operation, Other Income									(7,000)	135,000	147,000
Disposal Group, Including Discontinued Operation, Interest Expense									(413,000)	(2,195,000)	(3,874,000)
Discontinued Operation, Tax Effect of Discontinued Operation									8,848,000	67,005,000	28,743,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									(8,186,000)	(120,902,000)	(52,356,000)
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net					87,315,000					87,315,000
Disposal Group, Including Discontinued Operation, Inventory					62,663,000					62,663,000
Disposal Group, Including Discontinued Operation, Current Maturities of Long-Term Debt					0					0
Disposal Group, Including Discontinued Operation, Accounts Payable					77,287,000					77,287,000
Disposal Group, Including Discontinued Operation, Other Liabilities, Current					40,646,000					40,646,000
Disposal Group, Including Discontinued Operation, Long Term Debt Excluding Current Portion					0					0
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities, Noncurrent					(35,221,000)					(35,221,000)
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent					70,998,000					70,998,000
Disposal Group, Including Discontinued Operation, Liabilities					153,710,000					153,710,000
2015 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effect on Future Cash Flows, Amount									23,000,000
2016 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effect on Future Cash Flows, Amount									11,000,000
2017 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effect on Future Cash Flows, Amount									6,000,000
2018 - 2023 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Effect on Future Cash Flows, Amount									5,000,000
Oneok Partners [Member] | Natural Gas Distribution [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues									7,500,000	64,500,000	49,400,000
Oneok Partners [Member] | Energy Services [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Related Party Transaction, Other Revenues from Transactions with Related Party									$ 46,000,000	$ 276,300,000	$ 299,900,000