ONEOK (OKE) 10-K 25 Feb 20 2019 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2019	Feb. 18, 2020	Jun. 28, 2019
Cover page.
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-13643
Entity Registrant Name	ONEOK, Inc.
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1520922
Entity Address, Address Line One	100 West Fifth Street,
Entity Address, City or Town	Tulsa,
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	74103
City Area Code	918
Local Phone Number	588-7000
Title of 12(b) Security	Common stock, par value of $0.01
Trading Symbol	OKE
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 28.1
Entity Common Stock, Shares Outstanding		413,319,000
Documents Incorporated by Reference	Portions of the definitive proxy statement to be delivered to shareholders in connection with the Annual Meeting of Shareholders to be held May 20, 2020, are incorporated by reference in Part III.
Entity Central Index Key	0001039684
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues
Revenues	$ 10,164,367	$ 12,593,196	$ 12,173,907
Cost of sales and fuel (exclusive of items shown separately below)	6,788,040	9,422,708	9,538,045
Operations and maintenance	863,708	803,146	724,314
Depreciation and amortization	476,535	428,557	406,335
Impairment of long-lived assets (Note D)	0	0	15,970
General taxes	119,156	103,922	98,396
(Gain) loss on sale of assets	2,575	(601)	(924)
Operating income	1,914,353	1,835,464	1,391,771
Equity in net earnings from investments (Note M)	154,541	158,383	159,278
Impairment of equity investments (Note M)	0	0	(4,270)
Allowance for equity funds used during construction	64,815	7,962	107
Other income	27,058	674	15,385
Other expense	(18,003)	(14,928)	(35,812)
Interest expense (net of capitalized interest of $107,275, $28,062 and $5,510, respectively)	(491,773)	(469,620)	(485,658)
Income before income taxes	1,650,991	1,517,935	1,040,801
Income taxes (Note L)	(372,414)	(362,903)	(447,282)
Net income	1,278,577	1,155,032	593,519
Less: Net income attributable to noncontrolling interests	0	3,329	205,678
Net income attributable to ONEOK	1,278,577	1,151,703	387,841
Less: Preferred stock dividends	1,100	1,100	767
Net income available to common shareholders	$ 1,277,477	$ 1,150,603	$ 387,074
Basic earnings per common share (Note I)	$ 3.09	$ 2.80	$ 1.30
Diluted earnings per common share (Note I)	$ 3.07	$ 2.78	$ 1.29
Average shares (thousands)
Basic	413,560	411,485	297,477
Diluted	415,444	414,195	299,780
Commodity Sales
Revenues
Revenues	$ 8,916,047	$ 11,395,642	$ 9,862,652
Services
Revenues
Revenues	$ 1,248,320	$ 1,197,554	$ 2,311,255

CONSOLIDATED STATEMENTS OF IN_2

CONSOLIDATED STATEMENTS OF INCOME CONSOLIDATED STATEMENT OF INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Interest Expense (net of capitalized interest)	$ 107,275	$ 28,062	$ 5,510

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 320,251	$ 309,155	$ 311,963	$ 337,208	$ 292,888	$ 313,916	$ 282,179	$ 266,049	$ 1,278,577	$ 1,155,032	$ 593,519
Other comprehensive income (loss), net of tax
Change in fair value of derivatives, net of tax of $44,149, $1,694 and $19,006, respectively									(147,803)	(5,673)	(21,408)
Derivative amounts reclassified to net income, net of tax of $6,058, $(11,013) and $(26,899), respectively									(21,057)	36,870	63,687
Change in retirement and other postretirement benefit plan obligations, net of tax of $2,910, $(1,425) and $(878), respectively									(9,696)	4,771	(4,175)
Other comprehensive income (loss) of unconsolidated affiliates, net of tax of $2,152, $(724) and $145, respectively									(7,205)	2,424	(970)
Total other comprehensive income (loss), net of tax									(185,761)	38,392	37,134
Comprehensive income									1,092,816	1,193,424	630,653
Less: Comprehensive income attributable to noncontrolling interests									0	3,329	236,704
Comprehensive income attributable to ONEOK									$ 1,092,816	$ 1,190,095	$ 393,949

CONSOLIDATED STATEMENTS OF CO_2

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in fair value of derivatives, tax	$ 44,149	$ 1,694	$ 19,006
Derivative amounts reclassified to net income, tax	6,058	(11,013)	(26,899)
Change in retirement and other postretirement benefit plan obligations, tax	2,910	(1,425)	(878)
Other comprehensive income (loss) of unconsolidated affiliates, tax	$ 2,152	$ (724)	$ 145

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 20,958	$ 11,975
Accounts receivable, net	835,121	818,958
Materials and supplies	201,749	141,174
Natural gas and NGLs in storage	304,926	296,667
Commodity imbalances	25,267	29,050
Other current assets	82,313	100,808
Total current assets	1,470,334	1,398,632
Property, plant and equipment
Property, plant and equipment	22,051,492	18,030,963
Accumulated depreciation, depletion and amortization	3,702,807	3,264,312
Net property, plant and equipment (Note D)	18,348,685	14,766,651
Investments and other assets
Investments in unconsolidated affiliates	861,844	969,150
Goodwill and intangible assets (Note E)	957,833	967,142
Other assets	173,425	130,096
Total investments and other assets	1,993,102	2,066,388
Total assets	21,812,121	18,231,671
Current liabilities
Current maturities of long-term debt (Note F)	7,650	507,650
Short-term borrowings (Note F)	220,000	0
Accounts payable	1,209,900	1,116,337
Commodity imbalances	104,480	110,197
Accrued interest	190,750	161,377
Finance lease liability - current	1,949	1,765
Other current liabilities	285,569	211,110
Total current liabilities	2,020,298	2,108,436
Long-term debt, excluding current maturities (Note F)	12,479,757	8,873,334
Deferred credits and other liabilities
Deferred income taxes (Note L)	536,063	219,731
Finance lease liability (Note O)	24,296	26,244
Other deferred credits	525,756	424,383
Total deferred credits and other liabilities	1,086,115	670,358
Commitments and contingencies (Note N)
Equity (Note G)
Preferred stock, $0.01 par value: authorized and issued 20,000 shares at December 31, 2019, and at December 31, 2018	0	0
Common stock, $0.01 par value: authorized 1,200,000,000 shares; issued 445,016,234 shares and outstanding 413,239,050 shares at December 31, 2019; issued 445,016,234 shares and outstanding 411,532,606 shares at December 31, 2018	4,450	4,450
Paid-in capital	7,403,895	7,615,138
Accumulated other comprehensive loss (Note H)	(374,000)	(188,239)
Retained earnings	0	0
Treasury stock, at cost: 31,777,184 shares at December 31, 2019, and 33,483,628 shares at December 31, 2018	(808,394)	(851,806)
Total equity	6,225,951	6,579,543
Total liabilities and equity	$ 21,812,121	$ 18,231,671

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Equity (Note G)
Common stock, shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares, authorized (in shares)	1,200,000,000	1,200,000,000
Common stock, shares, issued (in shares)	445,016,234	445,016,234
Common stock, shares, outstanding (in shares)	413,239,050	411,532,606
Treasury stock, shares (in shares)	31,777,184	33,483,628
Preferred stock, shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares, issued (in shares)	20,000	20,000
Preferred stock, shares, authorized (in shares)	20,000	20,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 1,278,577	$ 1,155,032	$ 593,519
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	476,535	428,557	406,335
Impairment charges	0	0	20,240
Noncash contribution of preferred stock, net of tax	0	0	12,600
Equity in net earnings from investments	(154,541)	(158,383)	(159,278)
Distributions received from unconsolidated affiliates	163,476	170,528	167,372
Deferred Income Tax Expense (Benefit)	372,729	361,010	445,317
Deferred income taxes			437,917
Share-based compensation expense	37,147	31,664	26,262
Allowance for equity funds used during construction	(64,815)	(7,962)	(107)
Other, net	1,567	(132)	3,155
Changes in assets and liabilities:
Accounts receivable	(19,688)	383,993	(330,521)
Natural gas and NGLs in storage	(8,259)	38,456	(202,259)
Accounts payable	(62,946)	(320,132)	261,305
Commodity imbalances, net	(1,934)	(44,302)	43,699
Accrued interest	29,373	26,068	22,795
Risk-management assets and liabilities	(86,268)	117,717	37,617
Other assets and liabilities, net	(14,174)	4,605	(25,239)
Cash provided by operating activities	1,946,779	2,186,719	1,315,412
Investing activities
Capital expenditures (less allowance for equity funds used during construction)	(3,848,349)	(2,141,475)	(512,393)
Contributions to unconsolidated affiliates	(4,028)	(1,748)	(87,861)
Distributions received from unconsolidated affiliates in excess of cumulative earnings	94,168	26,757	28,742
Other, net	(10,549)	1,578	3,879
Cash used in investing activities	(3,768,758)	(2,114,888)	(567,633)
Financing activities
Dividends paid	(1,457,628)	(1,335,058)	(829,414)
Distributions to noncontrolling interests	0	(3,500)	(276,260)
Borrowing (repayment) of short-term borrowings, net	220,000	(614,673)	(495,604)
Issuance of long-term debt, net of discounts	4,185,435	1,795,773	1,190,496
Debt financing costs	(29,747)	(13,441)	(11,425)
Repayment of long-term debt	(1,057,348)	(932,650)	(994,776)
Issuance of common stock	29,040	1,203,981	471,358
Acquisition of noncontrolling interests	0	(195,000)	0
Other, net	(58,790)	(2,481)	(13,836)
Cash provided by (used in) financing activities	1,830,962	(97,049)	(959,461)
Change in cash and cash equivalents	8,983	(25,218)	(211,682)
Cash and cash equivalents at beginning of period	11,975	37,193	248,875
Cash and cash equivalents at end of period	20,958	11,975	37,193
Supplemental cash flow information:
Cash paid for interest, net of amounts capitalized	435,165	418,244	432,210
Cash paid for income taxes, net of refunds	$ 2,690	$ 2,225	$ 6,633

CONSOLIDATED STATEMENT OF CHANG

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Stock	Preferred Stock	Accumulated Other Comprehensive Loss	Retained Earnings	Additional Paid-in Capital [Member]	Treasury Stock	Noncontrolling Interests in Consolidated Subsidiaries
Shares, issued, beginning balance at Dec. 31, 2016		245,811,180,000	0
Total equity, beginning balance at Dec. 31, 2016	$ 3,428,915	$ 2,458	$ 0	$ (154,350)	$ 0	$ 1,234,314	$ (893,677)	$ 3,240,170
Net income	593,519	0	0	0	387,841	0	0	205,678
Other comprehensive income (loss)	37,134	0	0	6,108	0	0	0	31,026
Preferred Stock Issued During Period, Value, Other	20,000	0	0	0	0	20,000	0	0
Preferred stock dividends	(767)	$ 0	$ 0	0	0	(767)	0	0
Stock Issued During Period, Shares, Other		8,434,223,000	20,000,000
Stock Issued During Period, Value, Other	473,586	$ 85	$ 0	0	0	456,537	16,964	0
Common stock dividends	(828,787)	0	0	0	(461,209)	(367,578)	0	0
Distributions to noncontrolling interests	(276,260)	$ 0	0	0	0	0	0	(276,260)
Stock Issued During Period, Shares, Acquisitions		168,920,831,000
Acquisition of noncontrolling interests (Note G)	2,146,462	$ 1,689	0	(40,288)	0	5,228,580	0	(3,043,519)
Other, net	18,182	$ 0	$ 0	0	0	17,792	0	390
Shares, issued, ending balance at Dec. 31, 2017		423,166,234,000	20,000,000
Total equity, ending balance at Dec. 31, 2017	5,685,352	$ 4,232	$ 0	(188,530)	0	6,588,878	(876,713)	157,485
Cumulative effect adjustment for adoption of ASUs	73,368	0	0	0	73,368	0	0	0
Net income	1,155,032	0	0	0	1,151,703	0	0	3,329
Other comprehensive income (loss)	38,392	0	0	38,392	0	0	0	0
Preferred stock dividends	(1,100)	$ 0	0	0	(1,100)	0	0	0
Stock Issued During Period, Shares, Other		21,850,000,000
Stock Issued During Period, Value, Other	1,208,446	$ 218	0	0	0	1,183,321	24,907	0
Common stock dividends	(1,335,211)	0	0	0	(1,190,406)	(144,805)	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	0	0	(21,220)	0	(173,780)
Other, net	8,964	$ 0	$ 0	0	0	8,964	0	0
Shares, issued, ending balance at Dec. 31, 2018		445,016,234,000	20,000,000
Total equity, ending balance at Dec. 31, 2018	6,579,543	$ 4,450	$ 0	(188,239)	0	7,615,138	(851,806)	0
Cumulative effect adjustment for adoption of ASUs	1,719	0	0	(38,101)	39,803	0	0	17
Net income	1,278,577	0	0	0	1,278,577	0	0	0
Other comprehensive income (loss)	(185,761)	0	0	(185,761)	0	0	0	0
Preferred stock dividends	(1,100)	$ 0	0	0	(1,100)	0	0	0
Stock Issued During Period, Shares, Other		0
Stock Issued During Period, Value, Other	35,745	$ 0	0	0	0	(7,667)	43,412	0
Common stock dividends	(1,457,831)	0	0	0	(1,277,410)	(180,421)	0	0
Other, net	(23,155)	$ 0	$ 0	0	0	(23,155)	0	0
Shares, issued, ending balance at Dec. 31, 2019		445,016,234,000	20,000,000
Total equity, ending balance at Dec. 31, 2019	6,225,951	$ 4,450	$ 0	(374,000)	0	7,403,895	(808,394)	0
Cumulative effect adjustment for adoption of ASUs	$ (67)	$ 0	$ 0	$ 0	$ (67)	$ 0	$ 0	$ 0

CONSOLIDATED STATEMENT OF CHA_2

CONSOLIDATED STATEMENT OF CHANGES IN EQUITY CONSOLIDATED STATEMENT OF CHANGES IN EQUITY (Parenthetical) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Dividends paid (in dollars per share)	$ 3.53	$ 3.245	$ 2.72
Preferred stock dividends paid (in dollars per share)	$ 55	$ 55	$ 38.35

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Notes)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization and Nature of Operations - We are a corporation incorporated under the laws of the state of Oklahoma. Our Natural Gas Gathering and Processing segment provides midstream services to producers in North Dakota, Montana, Wyoming, Kansas and Oklahoma. Raw natural gas is typically gathered at the wellhead, compressed and transported through pipelines to our processing facilities. Processed natural gas, usually referred to as residue natural gas, is then recompressed and delivered to natural gas pipelines, storage facilities and end users. The NGLs separated from the raw natural gas are delivered through NGL pipelines to fractionation facilities for further processing. Our Natural Gas Liquids segment owns and operates facilities that gather, fractionate, treat and distribute NGLs and store NGL products, primarily in Oklahoma, Kansas, Texas, New Mexico and the Rocky Mountain region, which includes the Williston, Powder River and DJ Basins. We provide midstream services to producers of NGLs and deliver those products to the two primary market centers, one in the Mid-Continent in Conway, Kansas, and the other in the Gulf Coast in Mont Belvieu, Texas. The majority of the pipeline-connected natural gas processing plants in the Williston Basin, Oklahoma, Kansas and the Texas Panhandle are connected to our NGL gathering systems. We own or have an ownership interest in FERC-regulated NGL gathering and distribution pipelines in Oklahoma, Kansas, Texas, New Mexico, Montana, North Dakota, Wyoming and Colorado, and terminal and storage facilities in Missouri, Nebraska, Iowa and Illinois. We also own FERC-regulated NGL distribution and refined petroleum products pipelines in Kansas, Missouri, Nebraska, Iowa, Illinois and Indiana that connect our Mid-Continent assets with Midwest markets, including Chicago, Illinois. Our Natural Gas Pipelines segment provides interstate and intrastate transportation and storage services to end users through its wholly owned assets and its 50% ownership interests in Northern Border Pipeline and Roadrunner. Our interstate pipelines are regulated by the FERC and are located in North Dakota, Minnesota, Wisconsin, Illinois, Indiana, Kentucky, Tennessee, Oklahoma, Texas and New Mexico. Our intrastate natural gas pipeline and storage assets are located in Oklahoma, Kansas and Texas. Our assets connect major natural gas producing basins and market hubs with end-use customers. Consolidation - Our Consolidated Financial Statements include our accounts and the accounts of our subsidiaries over which we have control or are the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation. Investments in unconsolidated affiliates are accounted for using the equity method if we have the ability to exercise significant influence over operating and financial policies of our investee. Under this method, an investment is carried at its acquisition cost and adjusted each period for contributions made, distributions received and our share of the investee’s comprehensive income. For the investments we account for under the equity method, the premium or excess cost over underlying fair value of net assets is referred to as equity-method goodwill. Impairment of equity investments is recorded when the impairments are other than temporary. These amounts are recorded as investments in unconsolidated affiliates on our accompanying Consolidated Balance Sheets. See Note M for disclosures of our unconsolidated affiliates. Distributions paid to us from our unconsolidated affiliates are classified as operating activities on our Consolidated Statements of Cash Flows until the cumulative distributions exceed our proportionate share of income from the unconsolidated affiliate since the date of our initial investment. The amount of cumulative distributions paid to us that exceeds our cumulative proportionate share of income in each period represents a return of investment and is classified as an investing activity on our Consolidated Statements of Cash Flows. Use of Estimates - The preparation of our Consolidated Financial Statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amounts on our Consolidated Financial Statements. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets, liabilities and equity-method investments, obligations under employee benefit plans, provisions for uncollectible accounts receivable, expenses for services received but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts. In addition, a portion of our revenues and cost of sales and fuel are recorded based on current month prices and estimated volumes. The estimates are reversed in the following month and recorded with actual volumes and prices. We evaluate our estimates on an ongoing basis using historical experience, consultation with experts and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known. Fair Value Measurements - For our fair value measurements, we utilize market prices, third-party pricing services, present value methods and standard option valuation models to determine the price we would receive from the sale of an asset or the transfer of a liability in an orderly transaction at the measurement date. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date. Many of the contracts in our derivative portfolio are executed in liquid markets where price transparency exists. Our financial commodity derivatives are generally settled through a NYMEX or Intercontinental Exchange (ICE) clearing broker account with daily margin requirements. We validate our valuation inputs with third-party information and settlement prices from other sources, where available. We compute the fair value of our derivative portfolio by discounting the projected future cash flows from our derivative assets and liabilities to present value using interest-rate yields to calculate present-value discount factors derived from the implied forward LIBOR yield curve. The fair value of our forward-starting interest-rate swaps are determined using financial models that incorporate the implied forward LIBOR yield curve for the same period as the future interest-rate swap settlements. We consider current market data in evaluating counterparties’, as well as our own, nonperformance risk, net of collateral, by using counterparty-specific bond yields. Although we use our best estimates to determine the fair value of the derivative contracts we have executed, the ultimate market prices realized could differ materially from our estimates. Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below: • Level 1 - fair value measurements are based on unadjusted quoted prices for identical securities in active markets. These balances are composed predominantly of exchange-traded derivative contracts for natural gas and crude oil. • Level 2 - fair value measurements are based on significant observable pricing inputs, including quoted prices for similar assets and liabilities in active markets and inputs from third-party pricing services supported with corroborative evidence. These balances are composed of over-the-counter interest-rate derivatives. • Level 3 - fair value measurements are based on inputs that may include one or more unobservable inputs, including internally developed commodity price curves that incorporate market data from broker quotes and third-party pricing services. These balances are composed predominantly of exchange-cleared and over-the-counter derivatives to hedge NGL price risk and natural gas basis risk between various transaction locations and the NYMEX Henry Hub. Our commodity derivatives are generally valued using forward quotes provided by third-party pricing services that are validated with other market data. We believe any measurement uncertainty at December 31, 2019, is immaterial as our Level 3 fair value measurements are based on unadjusted pricing information from broker quotes and third-party pricing services. We do not believe that our Level 3 fair value estimates have a material impact on our results of operations, as our derivatives are accounted for as hedges. Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note B for our fair value measurements disclosures. Cash and Cash Equivalents - Cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less. Revenue Recognition - Revenues are recognized when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those goods or services. Our payment terms vary by customer and contract type, including requiring payment before products or services are delivered to certain customers. However, the term between customer prepayments, completion of our performance obligations, invoicing and receipt of payment due is not significant. A significant portion of supply volumes in our Natural Gas Gathering and Processing and Natural Gas Liquids segments are under contracts that include the purchase of commodities. Therefore, upon adoption of Topic 606, the contractual fees we charge on these contracts are considered a reduction of the commodity purchase price in cost of sales and fuel. In 2017 and prior periods, we recorded these fees as services revenue. See “Cost of Sales and Fuel” below for a description of these arrangements. Performance Obligations and Revenue Sources - Revenues sources are disaggregated in Note Q and are derived from commodity sales and services revenues, as described below: Commodity Sales (all segments) - We contract to deliver residue natural gas, condensate, unfractionated NGLs and/or NGL products to customers at a specified delivery point. Our sales agreements may be daily or longer-term contracts for a specified volume. We consider the sale and delivery of each unit of a commodity an individual performance obligation as the customer is expected to control, accept and benefit from each unit individually. We record revenue when the commodity is delivered to the customer as this represents the point in time when control of the product is transferred to the customer. Revenue is recorded based on the contracted selling price, which is generally index-based and settled monthly. Services Gathering only contracts ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we charge fees for providing midstream services, which include gathering and treating our customer’s natural gas. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. POP with fee contracts with producer take-in-kind rights ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we do not control the stream of unprocessed natural gas that we receive at the wellhead due to the producer’s take-in-kind rights. We purchase a portion of the raw natural gas stream, charge fees for providing midstream services, which include gathering, treating, compressing and processing our customer’s natural gas. After performing these services, we return primarily the residue natural gas to the producer, sell the remaining commodities and remit a portion of the commodity sales proceeds to the producer less our contractual fees. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Transportation and exchange contracts ( Natural Gas Liquids segment ) - Under this type of contract, we charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Our performance obligation begins with delivery of unfractionated NGLs or NGL products to our system. These services represent a series of distinct services that are treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. For transportation services under a tariff on our NGL transportation pipelines, fees are recorded upon redelivery to our customer at the completion of the transportation services. Storage contracts ( Natural Gas Liquids and Natural Gas Pipelines segments ) - We reserve a stated storage capacity and inject/withdraw/store commodities for our customer. The capacity reservation and injection/withdrawal/storage services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue as invoiced to our customers. For contracts that do not include a capacity reservation, transportation, injection and withdrawal fees are recognized in revenue as those services are provided and are dependent on the volume transported, injected or withdrawn by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Firm service transportation contracts ( Natural Gas Pipelines segment ) - We reserve a stated transportation capacity and transport commodities for our customer. The capacity reservation and transportation services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue based on a daily effective fee rate. If the capacity reservation fees vary solely as a contract feature, contract assets or liabilities are recorded for the difference between the amount recorded in revenue and the amount billed to the customer. Transportation fees are recognized in revenue as those services are provided and are dependent on the volume transported by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Interruptible transportation contracts ( Natural Gas Pipelines segment ) - We agree to transport natural gas on our pipelines between the customer’s specified nomination and delivery points if capacity is available after satisfying firm transportation service obligations. The transaction price is based on the transportation fees times the volumes transported. These fees may change over time based on an index or other factors provided in the agreement. We use the output method based on delivery of product to the customer to measure satisfaction of the performance obligation. The total consideration for delivered volumes is recorded in revenue at the time of delivery, when the customer obtains control. See Note P for our revenue disclosures. Contract Assets and Contract Liabilities - Contract assets and contract liabilities are recorded when the amount of revenue recognized from a contract with a customer differs from the amount billed to the customer and recorded in accounts receivable. Our contract asset balances at the beginning and end of the period primarily relate to our firm service transportation contracts with tiered rates. Our contract liabilities primarily represent deferred revenue on contributions in aid of construction received from customers for which revenue is recognized over the contract periods, which range from 5 to 10 years , and deferred revenue on NGL storage contracts for which revenue is recognized over a one-year term. Cost of Sales and Fuel - Cost of sales and fuel primarily includes (i) the cost of purchased commodities, including NGLs, natural gas and condensate, (ii) fees incurred for third-party transportation, fractionation and storage of commodities, (iii) fuel and power costs incurred to operate our own facilities that gather, process, transport and store commodities, and (iv) an offset from the contractual fees deducted from the cost of purchased commodities under the contract types below: POP with fee contracts with no producer take-in-kind rights (Natural Gas Gathering and Processing segment ) - We purchase raw natural gas and charge contractual fees for providing midstream services, which include gathering, treating, compressing and processing the producer’s natural gas. After performing these services, we sell the commodities and return a portion of the commodity sales proceeds to the producer less our contractual fees. Purchase with fee ( Natural Gas Liquids segment ) - Under this type of contract, we purchase raw, unfractionated NGLs at an index price and charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Operations and Maintenance - Operations and maintenance primarily includes (i) payroll and benefit costs, (ii) third-party costs for operations, maintenance and integrity management, regulatory compliance and environmental and safety, and (iii) other business related service costs. Accounts Receivable - Accounts receivable represent valid claims against nonaffiliated customers for products sold or services rendered, net of allowances for doubtful accounts. We assess the creditworthiness of our counterparties on an ongoing basis and require security, including prepayments and other forms of collateral, when appropriate. Outstanding customer receivables are reviewed regularly for possible nonpayment indicators, and allowances for doubtful accounts are recorded based upon management’s estimate of collectability at each balance sheet date. At December 31, 2019 and 2018 , our allowance for doubtful accounts was not material. Update - Upon adoption of ASU 2016-13 in January 2020, we are required to present accounts receivable net of an allowance for credit losses to reflect the net amount expected to be collected. This assessment is based on historical information, current conditions and supportable forecasts. See “Recently Issued Accounting Standards Update” table below for more information. Inventory - The values of current natural gas and NGLs in storage are determined using the lower of weighted-average cost or net realizable value. Noncurrent natural gas and NGLs are classified as property and valued at cost. Materials and supplies are valued at average cost. Commodity Imbalances - Commodity imbalances represent amounts payable or receivable for NGL exchange contracts and natural gas pipeline imbalances and are valued at market prices. Under the majority of our NGL exchange agreements, we physically receive volumes of unfractionated NGLs, including the risk of loss and legal title to such volumes, from the exchange counterparty. In turn, we deliver NGL products back to the customer and charge them gathering, transportation and fractionation fees. To the extent that the volumes we receive under such agreements differ from those we deliver, we record a net exchange receivable or payable position with the counterparties. These net exchange receivables and payables are generally settled with movements of NGL products rather than with cash. Natural gas pipeline imbalances are settled in cash or in-kind, subject to the terms of the pipelines’ tariffs or by agreement. Derivatives and Risk Management - We utilize derivatives to reduce our market-risk exposure to commodity price and interest-rate fluctuations and to achieve more predictable cash flows. We record all derivative instruments at fair value, with the exception of normal purchases and normal sales transactions that are expected to result in physical delivery. Commodity price and interest-rate volatility may have a significant impact on the fair value of derivative instruments as of a given date. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it. The table below summarizes the various ways in which we account for our derivative instruments and the impact on our Consolidated Financial Statements: Recognition and Measurement Accounting Treatment Balance Sheet Income Statement Normal purchases and normal sales - Fair value not recorded - Change in fair value not recognized in earnings Mark-to-market - Recorded at fair value - Change in fair value recognized in earnings Cash flow hedge - The gain or loss on the derivative instrument is reported initially as a component of accumulated other comprehensive income (loss) - The gain or loss on the derivative instrument is reclassified out of accumulated other comprehensive income (loss) into earnings when the forecasted transaction affects earnings Fair value hedge - Recorded at fair value - The gain or loss on the derivative instrument is recognized in earnings - Change in fair value of the hedged item is recorded as an adjustment to book value - Change in fair value of the hedged item is recognized in earnings To reduce our exposure to fluctuations in natural gas, NGLs and condensate prices, we periodically enter into futures, forward purchases and sales, options or swap transactions in order to hedge anticipated purchases and sales of natural gas, NGLs and condensate. Interest-rate swaps are used from time to time to manage interest-rate risk. Under certain conditions, we designate our derivative instruments as a hedge of exposure to changes in fair values or cash flows. We formally document all relationships between hedging instruments and hedged items, as well as risk-management objectives and strategies for undertaking various hedge transactions, and methods for assessing and testing correlation and hedge effectiveness. We specifically identify the forecasted transaction that has been designated as the hedged item in a cash flow hedge relationship. We assess the effectiveness of hedging relationships at inception of the hedge by performing an effectiveness analysis on our fair value and cash flow hedging relationships to determine whether the hedge relationships are highly effective. Subsequently we perform qualitative assessments. We also document our normal purchases and normal sales transactions that we expect to result in physical delivery and that we elect to exempt from derivative accounting treatment. The realized revenues and purchase costs of our derivative instruments not considered held for trading purposes and derivatives that qualify as normal purchases or normal sales that are expected to result in physical delivery are reported on a gross basis. Cash flows from futures, forwards, options and swaps that are accounted for as hedges are included in the same category as the cash flows from the related hedged items in our Consolidated Statements of Cash Flows. See Notes B and C for disclosures of our fair value measurements and risk-management and hedging activities. Property, Plant and Equipment - Our properties are stated at cost, including AFUDC and capitalized interest. In some cases, the cost of regulated property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or transfers of nonregulated properties or an entire operating unit or system of our regulated properties are recognized in income. Maintenance and repairs are charged directly to expense. The interest portion of AFUDC and capitalized interest represent the cost of borrowed funds used to finance construction activities for regulated and nonregulated projects, respectively. We capitalize interest costs during the construction or upgrade of qualifying assets. These costs are recorded as a reduction to interest expense. The equity portion of AFUDC represents the capitalization of the estimated average cost of equity used during the construction of major projects and is recorded in the cost of our regulated properties and as a credit to the allowance for equity funds used during construction. Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. For our regulated assets, these depreciation studies are completed as a part of our rate proceedings or tariff filings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved. For our nonregulated assets, if it is determined that the estimated economic life changes, the changes are made prospectively. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position or results of operations. Property, plant and equipment on our Consolidated Balance Sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use. See Note D for our property, plant and equipment disclosures. Impairment of Goodwill and Long-Lived Assets, Including Intangible Assets - We assess our goodwill for impairment at least annually on July 1, unless events or changes in circumstances indicate an impairment may have occurred before that time. Our qualitative goodwill impairment analysis performed as of July 1, 2019, did not result in an impairment charge nor did our analysis reflect any reporting units at risk, and subsequent to that date, no event has occurred indicating that the implied fair value of each of our reporting units is less than the carrying value of its net assets. As part of our goodwill impairment test, we may first assess qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance) to determine whether it is more likely than not that the fair value of each of our reporting units is less than its carrying amount. If further testing is necessary or a quantitative test is elected, we perform a two-step impairment test for goodwill. In the first step, an initial assessment is made by comparing the fair value of a reporting unit with its book value, including goodwill. If the fair value is less than the book value, an impairment is indicated, and we must perform a second test to measure the amount of the impairment. In the second test, we calculate the implied fair value of the goodwill by deducting the fair value of all tangible and intangible net assets of the reporting unit from the fair value determined in step one of the assessment. If the carrying value of the goodwill exceeds the implied fair value of the goodwill, we will record an impairment charge. Update - Upon adoption of ASU 2017-04 in January 2020, the requirement to calculate the implied fair value of goodwill under the two-step impairment test was eliminated. See “Recently Issued Accounting Standards Update” table below for more information. To estimate the fair value of our reporting units, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply EBITDA multiples to forecasted EBITDA. The multiples used are consistent with historical asset transactions. The forecasted cash flows are based on average forecasted cash flows for a reporting unit over a period of years. We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. For the investments we account for under the equity method, the impairment test considers whether the fair value of the equity investment as a whole, not the underlying net assets, has declined and whether that decline is other than temporary. Therefore, we periodically evaluate the amount at which we carry our equity-method investments to determine whether current events or circumstances warrant adjustments to our carrying values. See Notes D , E and M for our long-lived assets, goodwill and intangible assets and investments in unconsolidated affiliates disclosures. Regulation - Depending on the specific service provided, our natural gas transmission pipelines, NGL pipelines and certain natural gas storage facilities are subject to rate regulation and/or accounting requirements by one or more of the FERC, OCC, KCC and RRC. Accordingly, portions of our Natural Gas Liquids and Natural Gas Pipelines segments follow the accounting and reporting guidance for regulated operations. In our Consolidated Financial Statements and our Notes to Consolidated Financial Statements, regulated operations are defined pursuant to Financial Accounting Standards Board’s (FASB) ASC 980, Regulated Operations. During the rate-making process for certain of our assets, regulatory authorities set the framework for what we can charge customers for our services and establish the manner that our costs are accounted for, including allowing us to defer recognition of certain costs and permitting recovery of the amounts through rates over time as opposed to expensing such costs as incurred. Certain examples of types of regulatory guidance include costs for fuel and losses, acquisition costs, contributions in aid of construction, charges for depreciation, and gains or losses on disposition of assets. This allows us to stabilize rates over time rather than passing such costs on to the customer for immediate recovery. Actions by regulatory authorities could have an effect on the amounts we may charge our customers. Any difference in the amount recoverable and the amount deferred is recorded as income or expense at the time of the re

FAIR VALUE MEASUREMENTS (Notes)

FAIR VALUE MEASUREMENTS (Notes)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Recurring Fair Value Measurements - The following tables set forth our recurring fair value measurements for the periods indicated: December 31, 2019 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,892 $ — $ 55,557 $ 66,449 $ (28,588 ) $ 37,861 Interest-rate contracts — 581 — 581 — 581 Total derivative assets $ 10,892 $ 581 $ 55,557 $ 67,030 $ (28,588 ) $ 38,442 Derivative liabilities Commodity contracts Financial contracts $ (4,811 ) $ — $ (24,785 ) $ (29,596 ) $ 28,588 $ (1,008 ) Interest-rate contracts — (201,941 ) — (201,941 ) — (201,941 ) Total derivative liabilities $ (4,811 ) $ (201,941 ) $ (24,785 ) $ (231,537 ) $ 28,588 $ (202,949 ) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2019 , we held no cash and posted $8.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet. December 31, 2018 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,812 $ — $ 69,165 $ 79,977 $ (32,739 ) $ 47,238 Physical contracts — — 1,142 1,142 — 1,142 Interest-rate contracts — 19,005 — 19,005 — 19,005 Total derivative assets $ 10,812 $ 19,005 $ 70,307 $ 100,124 $ (32,739 ) $ 67,385 Derivative liabilities Commodity contracts Financial contracts $ (2,916 ) $ — $ (29,823 ) $ (32,739 ) $ 32,739 $ — Interest-rate contracts — (99,260 ) — (99,260 ) — (99,260 ) Total derivative liabilities $ (2,916 ) $ (99,260 ) $ (29,823 ) $ (131,999 ) $ 32,739 $ (99,260 ) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2018 , we held no cash and posted $0.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet. The following table sets forth a reconciliation of our Level 3 fair value measurements for the periods indicated: Years Ended December 31, Derivative Assets (Liabilities) 2019 2018 ( Thousands of dollars ) Net assets (liabilities) at beginning of period $ 40,484 $ (32,838 ) Total changes in fair value: Gains (losses) included in net income (a) — (140 ) Settlements included in net income (a) (40,344 ) 29,141 New Level 3 derivatives included in other comprehensive income (loss) (b) 30,627 37,106 Unrealized change included in other comprehensive income (loss) (b) 5 7,215 Net assets (liabilities) at end of period $ 30,772 $ 40,484 (a) - Included in commodity sales revenues/cost of sales and fuel in our Consolidated Statements of Income. (b) - Included in change in fair value of derivatives in our Consolidated Statements of Comprehensive Income. During the years ended December 31, 2019 and 2018 , there were no transfers in or out of Level 3 of the fair value hierarchy. Other Financial Instruments - The approximate fair value of cash and cash equivalents, accounts receivable, accounts payable and short-term borrowings is equal to book value due to the short-term nature of these items. Our cash and cash equivalents are composed of bank and money market accounts and are classified as Level 1. Our short-term borrowings are classified as Level 2 since the estimated fair value of the short-term borrowings can be determined using information available in the commercial paper market. The estimated fair value of our consolidated long-term debt, including current maturities, was $13.8 billion and $9.6 billion at December 31, 2019 and 2018 , respectively. The book value of our consolidated long-term debt, including current maturities, was $12.5 billion and $9.4 billion at December 31, 2019 and 2018 , respectively. The estimated fair value of the aggregate senior notes outstanding was determined using quoted market prices for similar issues with similar terms and maturities. The estimated fair value of our consolidated long-term debt is classified as Level 2.

RISK MANAGEMENT AND HEDGING ACT

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES (Notes)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES	RISK-MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES Risk-management Activities - We are sensitive to changes in natural gas, crude oil and NGL prices, principally as a result of contractual terms under which these commodities are processed, purchased and sold. We are also subject to the risk of interest-rate fluctuation in the normal course of business. We use physical-forward purchases and sales and financial derivatives to secure a certain price for a portion of our natural gas, condensate and NGL products; to reduce our exposure to commodity price and interest-rate fluctuations; and to achieve more predictable cash flows. We follow established policies and procedures to assess risk and approve, monitor and report our risk-management activities. We have not used these instruments for trading purposes. Commodity price risk - Commodity price risk refers to the risk of loss in cash flows and future earnings arising from adverse changes in the price of natural gas, NGLs and condensate. We may use the following commodity derivative instruments to reduce the near-term commodity price risk associated with a portion of the forecasted sales of these commodities: • Futures contracts - Standardized contracts to purchase or sell natural gas and crude oil for future delivery or settlement under the provisions of exchange regulations; • Forward contracts - Nonstandardized commitments between two parties to purchase or sell natural gas, crude oil or NGLs for future physical delivery. These contracts are typically nontransferable and can only be canceled with the consent of both parties; • Swaps - Exchange of one or more payments based on the value of one or more commodities. These instruments transfer the financial risk associated with a future change in value between the counterparties of the transaction, without also conveying ownership interest in the asset or liability; and • Options - Contractual agreements that give the holder the right, but not the obligation, to buy or sell a fixed quantity of a commodity at a fixed price within a specified period of time. Options may either be standardized and exchange-traded or customized and nonexchange-traded. We may also use other instruments including collars to mitigate commodity price risk. A collar is a combination of a purchased put option and a sold call option, which places a floor and a ceiling price for commodity sales being hedged. In our Natural Gas Gathering and Processing segment, we are exposed to commodity price risk as a result of retaining a portion of the commodity sales proceeds associated with our POP with fee contracts. Under certain POP with fee contracts, our fees and POP percentage may increase or decrease if production volumes, delivery pressures or commodity prices change relative to specified thresholds. We also are exposed to basis risk between the various production and market locations where we buy and sell commodities. As part of our hedging strategy, we use the previously described commodity derivative financial instruments and physical-forward contracts to reduce the impact of price fluctuations related to natural gas, NGLs and condensate. In our Natural Gas Liquids segment, we are primarily exposed to commodity price risk resulting from the relative values of the various NGL products to each other, the value of NGLs in storage and the relative value of NGLs to natural gas. We are also exposed to location price differential risk as a result of the relative value of NGL purchases at one location and sales at another location, primarily related to our optimization and marketing business. As part of our hedging strategy, we utilize physical-forward contracts and commodity derivative financial instruments to reduce the impact of price fluctuations related to NGLs. In our Natural Gas Pipelines segment, we are exposed to commodity price risk because our intrastate and interstate pipelines consume natural gas in operations and retain natural gas from our customers for operations or as part of our fee for services provided. When the amount consumed in operations differs from the amount provided by our customers, our pipelines must buy or sell natural gas, or store or use natural gas from inventory, which can expose this segment to commodity price risk depending on the regulatory treatment for this activity. To the extent that commodity price risk in our Natural Gas Pipelines segment is not mitigated by fuel cost-recovery mechanisms, we may use physical-forward sales or purchases to reduce the impact of natural gas price fluctuations. At December 31, 2019 and 2018 , there were no financial derivative instruments with respect to our natural gas pipeline operations. Interest-rate risk - We manage interest-rate risk through the use of fixed-rate debt, floating-rate debt and interest-rate swaps. Interest-rate swaps are agreements to exchange interest payments at some future point based on specified notional amounts. In 2019, we entered into $625 million of forward-starting interest-rate swaps to hedge the variability of interest payments on a portion of our forecasted debt issuances that may result from changes in the benchmark interest rate before the debt is issued. We also settled $1.8 billion of our forward-starting interest-rate swaps related to our underwritten public offering of $1.25 billion senior unsecured notes in March 2019 and $2.0 billion senior unsecured notes in August 2019. At December 31, 2019 and 2018, we had forward-starting interest-rate swaps with notional amounts totaling $1.8 billion and $3.0 billion , respectively, to hedge the variability of interest payments on a portion of our forecasted debt issuances. At December 31, 2019 and 2018, we had interest-rate swaps with notional amounts totaling $1.3 billion to hedge the variability of our LIBOR-based interest payments. All of our interest-rate swaps are designated as cash flow hedges. Fair Values of Derivative Instruments - All derivatives measured at fair value at December 31, 2019 and 2018, were designated as hedging instruments. See Note B for a discussion of the inputs associated with our fair value measurements. The following table sets forth the fair values of our derivative instruments presented on a gross basis for the periods indicated: December 31, 2019 December 31, 2018 Location in our Consolidated Balance Sheets Assets (Liabilities) Assets (Liabilities) ( Thousands of dollars ) Derivatives designated as hedging instruments Commodity contracts (a) Financial contracts Other current assets $ 64,858 $ (26,997 ) $ 78,891 $ (31,793 ) Other assets/other deferred credits 1,591 (2,599 ) 1,086 (946 ) Physical contracts Other current assets — — 1,142 — Interest-rate contracts Other current assets/other current liabilities — (90,161 ) 19,005 (15,012 ) Other assets/other deferred credits 581 (111,780 ) — (84,248 ) Total derivatives designated as hedging instruments $ 67,030 $ (231,537 ) $ 100,124 $ (131,999 ) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheets on a net basis when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. Notional Quantities for Derivative Instruments - The following table sets forth the notional quantities for derivative instruments held for the periods indicated: December 31, 2019 December 31, 2018 Contract Type Purchased/ Payor Sold/ Receiver Purchased/ Payor Sold/ Receiver Derivatives designated as hedging instruments: Cash flow hedges Fixed price -Natural gas ( Bcf ) Futures and swaps — (59.0 ) — (29.9 ) -Crude oil and NGLs ( MMBbl ) Futures, forwards and swaps 7.9 (17.4 ) 6.5 (13.8 ) Basis -Natural gas ( Bcf ) Futures and swaps — (59.0 ) — (29.9 ) Interest-rate contracts ( Billions of dollars ) Swaps $ 3.1 $ — $ 4.3 $ — These notional amounts are used to summarize the volume of financial instruments; however, they do not reflect the extent to which the positions offset one another and, consequently, do not reflect our actual exposure to market or credit risk. Cash Flow Hedges - The following table sets forth the unrealized change in fair value of cash flow hedges in other comprehensive income (loss) for the periods indicated: Derivatives in Cash Flow Hedging Relationships Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Commodity contracts $ 38,819 $ 53,217 $ (40,577 ) Interest-rate contracts (230,771 ) (60,584 ) 163 Total unrealized change in fair value of cash flow hedges in other comprehensive income (loss) $ (191,952 ) $ (7,367 ) $ (40,414 ) The following table sets forth the effect of cash flow hedges on net income for the periods indicated: Derivatives in Cash Flow Hedging Relationships Location of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Net Income Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Commodity contracts Commodity sales revenues/cost of sales and fuel $ 50,345 $ (29,596 ) $ (69,561 ) Interest-rate contracts Interest expense (23,230 ) (18,287 ) (21,025 ) Total change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives $ 27,115 $ (47,883 ) $ (90,586 ) Credit Risk - We monitor the creditworthiness of our counterparties and compliance with policies and limits established by our Risk Oversight and Strategy Committee. We maintain credit policies with regard to our counterparties that we believe minimize overall credit risk. These policies include an evaluation of potential counterparties’ financial condition (including credit ratings, bond yields and credit default swap rates), collateral requirements under certain circumstances and the use of standardized master-netting agreements that allow us to net the positive and negative exposures associated with a single counterparty. We use internally developed credit ratings for counterparties that do not have a credit rating. Our financial commodity derivatives are generally settled through a NYMEX or Intercontinental Exchange (ICE) clearing broker account with daily margin requirements. However, we may enter into financial derivative instruments that contain provisions that require us to maintain an investment-grade credit rating from S&P and/or Moody’s. If our credit ratings on our senior unsecured long-term debt were to decline below investment grade, the counterparties to the derivative instruments could request collateralization on derivative instruments in net liability positions. There were no financial derivative instruments with contingent features related to credit risk at December 31, 2019 . The counterparties to our derivative contracts typically consist of major energy companies, financial institutions and commercial and industrial end users. This concentration of counterparties may affect our overall exposure to credit risk, either positively or negatively, in that the counterparties may be affected similarly by changes in economic, regulatory or other conditions. Based on our policies, exposures, credit and other reserves, we do not anticipate a material adverse effect on our financial position or results of operations as a result of counterparty nonperformance. At December 31, 2019 , the net credit exposure from our derivative assets is with investment-grade companies in the financial services sector.

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Notes)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
PROPERTY, PLANT AND EQUIPMENT	PROPERTY, PLANT AND EQUIPMENT The following table sets forth our property, plant and equipment by property type, for the periods indicated: Estimated Useful Lives (Years) December 31, December 31, ( Thousands of dollars ) Nonregulated Gathering pipelines and related equipment 5 to 40 $ 4,316,936 $ 3,851,043 Processing and fractionation and related equipment 3 to 40 4,439,332 4,171,072 Storage and related equipment 3 to 54 684,635 656,455 Transmission pipelines and related equipment 5 to 54 797,678 782,258 General plant and other 2 to 60 610,013 547,424 Construction work in process — 1,645,663 797,182 Regulated Storage and related equipment 5 to 25 9,180 8,987 Natural gas transmission pipelines and related equipment 5 to 77 1,552,546 1,475,789 NGL transmission pipelines and related equipment 5 to 88 6,126,056 4,677,599 General plant and other 2 to 50 66,507 61,136 Construction work in process — 1,802,946 1,002,018 Property, plant and equipment 22,051,492 18,030,963 Accumulated depreciation and amortization - nonregulated (2,471,649 ) (2,168,855 ) Accumulated depreciation and amortization - regulated (1,231,158 ) (1,095,457 ) Net property, plant and equipment $ 18,348,685 $ 14,766,651 The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated: Years Ended December 31, 2019 2018 2017 Natural Gas Liquids 2.0% 1.9% 1.9% Natural Gas Pipelines 2.1% 2.1% 2.1% We incurred costs for construction work in process that had not been paid at December 31, 2019, 2018 and 2017 , of $544.8 million , $388.3 million and $92.4 million , respectively. Such amounts are not included in capital expenditures (less AFUDC and capitalized interest) on the Consolidated Statements of Cash Flows. Impairment Charges - In 2017, following a review of nonstrategic assets for potential divestiture, we recorded $16.0 million of noncash impairment charges related to certain nonstrategic gathering and processing assets located in North Dakota.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Notes)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS Goodwill - The following table sets forth our goodwill, by segment, for the periods indicated: December 31, December 31, ( Thousands of dollars ) Natural Gas Gathering and Processing $ 153,404 $ 153,404 Natural Gas Liquids 371,217 371,217 Natural Gas Pipelines 156,375 156,479 Total goodwill $ 680,996 $ 681,100 Intangible Assets - Our intangible assets relate primarily to contracts acquired through acquisitions in our Natural Gas Gathering and Processing and Natural Gas Liquids segments, which are being amortized over periods of 15 to 40 years. Amortization expense for intangible assets was $11.9 million in 2019, 2018 and 2017, and the aggregate amortization expense for each of the next five years is estimated to be $ 11.9 million . The following table reflects the gross carrying amount and accumulated amortization of intangible assets for the periods presented: December 31, December 31, ( Thousands of dollars ) Gross intangible assets $ 414,345 $ 411,650 Accumulated amortization (137,508 ) (125,608 ) Net intangible assets $ 276,837 $ 286,042

DEBT (Notes)

DEBT (Notes)	12 Months Ended
	Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]
DEBT	DEBT The following table sets forth our consolidated debt for the periods indicated: December 31, December 31, (Thousands of dollars) Commercial paper outstanding, bearing a weighted-average interest rate of 2.16% as of December 31, 2019 $ 220,000 $ — Senior unsecured obligations: $500,000 at 8.625% due March 2019 — 500,000 $300,000 at 3.8% due March 2020 — 300,000 $1,500,000 term loan, rate of 2.70% and 3.63% as of December 31, 2019 and 2018, respectively, due November 2021 1,250,000 550,000 $700,000 at 4.25% due February 2022 547,397 547,397 $900,000 at 3.375 % due October 2022 900,000 900,000 $425,000 at 5.0 % due September 2023 425,000 425,000 $500,000 at 7.5% due September 2023 500,000 500,000 $500,000 at 2.75% due September 2024 500,000 — $500,000 at 4.9 % due March 2025 500,000 500,000 $500,000 at 4.0% due July 2027 500,000 500,000 $800,000 at 4.55% due July 2028 800,000 800,000 $100,000 at 6.875% due September 2028 100,000 100,000 $700,000 at 4.35% due March 2029 700,000 — $750,000 at 3.4% due September 2029 750,000 — $400,000 at 6.0% due June 2035 400,000 400,000 $600,000 at 6.65% due October 2036 600,000 600,000 $600,000 at 6.85% due October 2037 600,000 600,000 $650,000 at 6.125% due February 2041 650,000 650,000 $400,000 at 6.2% due September 2043 400,000 400,000 $700,000 at 4.95% due July 2047 700,000 700,000 $1,000,000 at 5.2% due July 2048 1,000,000 450,000 $750,000 at 4.45% due September 2049 750,000 — Guardian Pipeline Weighted average 7.85% due December 2022 21,307 28,957 Total debt 12,813,704 9,451,354 Unamortized portion of terminated swaps 15,032 16,750 Unamortized debt issuance costs and discounts (121,329 ) (87,120 ) Current maturities of long-term debt (7,650 ) (507,650 ) Short-term borrowings (a) (220,000 ) — Long-term debt $ 12,479,757 $ 8,873,334 (a) - Individual issuances of commercial paper under our commercial paper program generally mature in 90 days or less. $2.5 Billion Credit Agreement - In May 2019, we extended the term of our $2.5 Billion Credit Agreement by one year to June 2024. Our $2.5 Billion Credit Agreement is a revolving credit facility and contains certain financial, operational and legal covenants. Among other things, these covenants include maintaining a ratio of indebtedness to adjusted EBITDA (EBITDA, as defined in our $2.5 Billion Credit Agreement, adjusted for all noncash charges and increased for projected EBITDA from certain lender-approved capital expansion projects) of no more than 5.0 to 1 at December 31, 2019. If we consummate one or more acquisitions in which the aggregate purchase is $25 million or more, the allowable ratio of indebtedness to adjusted EBITDA will increase to 5.5 to 1 for the quarter in which the acquisition is completed and the following two quarters. Thereafter, the covenant will decrease to 5.0 to 1. Our $2.5 Billion Credit Agreement includes a $100 million sublimit for the issuance of standby letters of credit and a $200 million sublimit for swingline loans. Under the terms of our $2.5 Billion Credit Agreement, we may request an increase in the size of the facility to an aggregate of $3.5 billion by either commitments from new lenders or increased commitments from existing lenders. Our $2.5 Billion Credit Agreement contains provisions for an applicable margin rate and an annual facility fee, both of which adjust with changes in our credit ratings. Based on our current credit ratings, borrowings, if any, will accrue at LIBOR plus 110 basis points, and the annual facility fee is 15 basis points. At December 31, 2019, our ratio of indebtedness to adjusted EBITDA was 4.1 to 1, and we were in compliance with all covenants under our $2.5 Billion Credit Agreement. At December 31, 2019 and 2018, we had letters of credit issued totaling $4.7 million and $1.4 million , respectively, and no borrowings outstanding under our $2.5 Billion Credit Agreement. Senior Unsecured Obligations - All notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness, and are structurally subordinate to any of the existing and future debt and other liabilities of any nonguarantor subsidiaries. Issuances - In August 2019, we completed an underwritten public offering of $2.0 billion senior unsecured notes consisting of $500 million , 2.75% senior notes due 2024; $750 million , 3.4% senior notes due 2029; and $750 million , 4.45% senior notes due 2049. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.97 billion . The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In March 2019, we completed an underwritten public offering of $1.25 billion senior unsecured notes consisting of $700 million , 4.35% senior notes due 2029 and an additional issuance of $550 million of our existing 5.2% senior notes due 2048. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, and exclusive of accrued interest, were $1.23 billion . The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In November 2018, we entered into our $1.5 Billion Term Loan Agreement with a syndicate of banks, which was fully drawn as of June 30, 2019. We repaid $250 million of our outstanding balance in August 2019 and have $1.25 billion drawn as of December 31, 2019. Our $1.5 Billion Term Loan Agreement matures in November 2021 and bears interest at LIBOR plus 112.5 basis points based on our current credit ratings. The agreement contains an option, which may be exercised up to two times, to extend the term of the loan, in each case, for an additional one-year term subject to approval of the banks. Our $1.5 Billion Term Loan Agreement allows prepayment of all or any portion outstanding, without penalty or premium, and contains substantially the same covenants as those contained in our $2.5 Billion Credit Agreement. The proceeds were used for general corporate purposes, including repayment of existing indebtedness and funding capital expenditures. In July 2018, we completed an underwritten public offering of $1.25 billion senior unsecured notes consisting of $800 million , 4.55% senior notes due 2028 and $450 million , 5.2% senior notes due 2048. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.23 billion . The proceeds were used for general corporate purposes, which included repayment of existing indebtedness and funding capital expenditures. In July 2017, we completed an underwritten public offering of $1.2 billion senior unsecured notes consisting of $500 million , 4.0% senior notes due 2027, and $700 million , 4.95% senior notes due 2047. The net proceeds, after deducting underwriting discounts, commissions and offering expenses, were $1.2 billion . The proceeds were used for general corporate purposes, which included repayment of existing indebtedness and funding capital expenditures. Repayments - In September 2019, we redeemed our $300 million , 3.8% senior notes due March 2020 at a redemption price of $308.0 million , including the outstanding principal, plus accrued and unpaid interest, with cash on hand from our public offering of $2.0 billion senior unsecured notes in August 2019. In connection with this early redemption, we incurred a $2.7 million loss on extinguishment of debt, which is included in other expense in our Consolidated Statements of Income for the year ended December 31, 2019. In August 2019, we repaid $250 million of our $1.5 Billion Term Loan agreement with cash on hand. In March 2019, we repaid our $500 million , 8.625% senior notes at maturity with a combination of cash on hand and short-term borrowings. In 2018, we repaid our $425 million , 3.2% senior notes due September 2018 with cash on hand and the remaining $500 million of the ONEOK Partners Term Loan Agreement due 2019 with a combination of cash on hand and short-term borrowings. In 2017, we repaid ONEOK Partners’ $400 million , 2.0% senior notes due in October 2017 and repaid $500 million of the ONEOK Partners Term Loan Agreement due 2019 with a combination of cash on hand and short-term borrowings and redeemed our 6.5% senior notes due 2028 at a redemption price of $87.0 million with cash on hand. The aggregate maturities of long-term debt outstanding as of December 31, 2019, for the years 2020 through 2024 are shown below: Senior Unsecured Obligations Guardian Pipeline Total (Millions of dollars) 2020 $ — $ 7.7 $ 7.7 2021 $ 1,250.0 $ 7.7 $ 1,257.7 2022 $ 1,447.4 $ 5.9 $ 1,453.3 2023 $ 925.0 $ — $ 925.0 2024 $ 500.0 $ — $ 500.0 Covenants - Our senior notes are governed by indentures containing covenants, including among other provisions, limitations on our ability to place liens on our property or assets and to sell and leaseback our property. The indentures governing our 6.875% senior notes due 2028 include an event of default upon acceleration of other indebtedness of $15 million or more, and the indentures governing the remainder of our senior notes include an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25% in aggregate principal amount of the outstanding senior notes to declare those senior notes immediately due and payable in full. The indenture for the 7.5% notes due 2023 also contains a provision that allows the holders of the notes to require ONEOK to offer to repurchase all or any part of their notes if a change of control and a credit rating downgrade occur at a purchase price of 101% of the principal amount, plus accrued and unpaid interest, if any. We may redeem our senior notes, in whole or in part, at any time prior to their maturity at a redemption price equal to the principal amount, plus accrued and unpaid interest and a make-whole premium. We may redeem the balance of our senior notes due 2022, 2023, 2024, 2025, 2027, 2028 (4.55%), 2029, 2041, 2043, 2047, 2048 and 2049 at a redemption price equal to the principal amount, plus accrued and unpaid interest, starting one to six months before the maturity date as stipulated in the respective contract terms. Our senior notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness. Guardian Pipeline Senior Notes - These senior notes were issued under a master shelf agreement dated November 8, 2001, with certain financial institutions. Principal payments are due quarterly through 2022. Guardian Pipeline’s senior notes contain financial covenants that require the maintenance of certain financial ratios as defined in the master shelf agreement based on Guardian Pipeline’s financial position and results of operations. Upon any breach of these covenants, all amounts outstanding under the master shelf agreement may become due and payable immediately . At December 31, 2019, Guardian Pipeline was in compliance with its financial covenants . Other - We amortize premiums, discounts and expenses incurred in connection with the issuance of long-term debt consistent with the terms of the respective debt instrument. Debt Guarantees - ONEOK, ONEOK Partners and the Intermediate Partnership have cross guarantees in place for our and ONEOK Partners’ indebtedness.

EQUITY EQUITY (Notes)

EQUITY EQUITY (Notes)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
EQUITY	EQUITY Noncontrolling Interests - As a result of the Merger Transaction in 2017, we and our subsidiaries own 100% of ONEOK Partners. The earnings of ONEOK Partners that are attributed to its units held by the public until June 30, 2017, are reported as “Net income attributable to noncontrolling interest” in our accompanying Consolidated Statements of Income. ONEOK Partners’ cash distributions paid prior to the Merger Transaction are reported as “Distributions to noncontrolling interests” in our accompanying Consolidated Statements of Changes in Equity. In July 2018, we acquired the remaining 20% interest in WTLPG for $195 million with cash on hand. We are now the sole owner of the West Texas LPG pipeline system. Series A and B Convertible Preferred Stock - There are no shares of Series A or Series B Preferred Stock currently issued or outstanding. Series E Preferred Stock - In April 2017, through a wholly owned subsidiary, we contributed 20,000 shares of newly issued Series E Preferred Stock, having an aggregate value of $20 million , to the Foundation for use in charitable and nonprofit causes. The contribution was recorded as a $20 million noncash expense in 2017, which represents a noncash financing activity, and is included in other expense in our Consolidated Statements of Income. Equity Issuances - In January 2018, we completed an underwritten public offering of 21.9 million shares of our common stock at a public offering price of $54.50 per share, generating net proceeds of $1.2 billion . We used the net proceeds from this offering to fund capital expenditures and for general corporate purposes, which included repaying a portion of our outstanding indebtedness. In July 2017, we established an “at-the-market” equity program for the offer and sale from time to time of our common stock up to an aggregate amount of $1 billion . The program allows us to offer and sell our common stock at prices we deem appropriate through a sales agent. Sales of our common stock may be made by means of ordinary brokers’ transactions on the NYSE, in block transactions, or as otherwise agreed to between us and the sales agent. We are under no obligation to offer and sell common stock under the program. No shares were sold through our “at-the-market” equity program in 2019 or 2018. During the year ended December 31, 2017, we sold 8.4 million shares of common stock through our “at-the-market” equity program that resulted in net proceeds of $448.3 million . The net proceeds from these issuances were used for general corporate purposes, including repayment of outstanding indebtedness and to fund capital expenditures. Dividends - Holders of our common stock share equally in any dividend declared by our Board of Directors, subject to the rights of the holders of outstanding preferred stock. Dividends paid totaled $1.5 billion , $1.3 billion and $829.4 million for 2019, 2018 and 2017 , respectively. In addition to the increase in dividends paid per share outlined in the table below, dividends paid increased due to the increase in number of shares outstanding as a result of the closing of the Merger Transaction and our equity issuances. The following table sets forth the quarterly dividends per share paid on our common stock in the periods indicated: Years Ended December 31, 2019 2018 2017 First Quarter $ 0.860 $ 0.770 $ 0.615 Second Quarter 0.865 0.795 0.615 Third Quarter 0.890 0.825 0.745 Fourth Quarter 0.915 0.855 0.745 Total $ 3.53 $ 3.245 $ 2.72 Additionally, in February 2020, we paid a quarterly dividend of $0.935 per share ( $3.74 per share on an annualized basis), which was paid to shareholders of record as of January 27, 2020 . The Series E Preferred Stock pays quarterly dividends on each share of Series E Preferred Stock, when, as and if declared by our Board of Directors, at a rate of 5.5% per year. We paid dividends for the Series E Preferred Stock of $1.1 million in both 2019 and 2018 and $0.6 million in 2017. We paid quarterly dividends totaling $0.3 million

ACCUMULATED OTHER COMPREHENSIVE

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Notes)	12 Months Ended
	Dec. 31, 2019
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	ACCUMULATED OTHER COMPREHENSIVE LOSS The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated: Risk- Management Assets/Liabilities (a) Retirement and Other Postretirement Benefit Plan Obligations (a) (b) Risk- Management Assets/Liabilities of Unconsolidated Affiliates (a) Accumulated Other Comprehensive Loss (a) ( Thousands of dollars ) January 1, 2018 $ (81,915 ) $ (105,411 ) $ (1,204 ) $ (188,530 ) Beginning balance adjustments (c) 3,078 (805 ) (2,273 ) — Other comprehensive income (loss) before reclassifications (5,673 ) (8,116 ) 2,396 (11,393 ) Amounts reclassified to net income 36,870 12,887 28 49,785 Other comprehensive income (loss) attributable to ONEOK 31,197 4,771 2,424 38,392 Impact of adoption of ASU 2018-02 (d) (17,020 ) (20,340 ) (741 ) (38,101 ) December 31, 2018 (64,660 ) (121,785 ) (1,794 ) (188,239 ) Other comprehensive loss before reclassifications (147,803 ) (19,490 ) (7,275 ) (174,568 ) Amounts reclassified to net income (21,057 ) 9,794 70 (11,193 ) Other comprehensive income (loss) (168,860 ) (9,696 ) (7,205 ) (185,761 ) December 31, 2019 $ (233,520 ) $ (131,481 ) $ (8,999 ) $ (374,000 ) (a) All amounts are presented net of tax. (b) Includes amounts related to supplemental executive retirement plan. (c) Reclassifications were made between categories to conform to current presentation. (d) We elected to adopt this guidance in the first quarter 2018, which allows a reclassification from accumulated other comprehensive income/loss to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act. After adopting and applying this guidance, our accumulated other comprehensive loss balance does not include stranded taxes resulting from the Tax Cuts and Jobs Act. The following table sets forth information about the balance of accumulated other comprehensive loss at December 31, 2019, representing unrealized gains (losses) related to risk-management assets and liabilities: Risk- Management Assets/Liabilities (a) ( Thousands of dollars ) Commodity derivative instruments expected to be realized within the next 24 months (b) $ 28,119 Settled interest-rate swaps to be recognized over the life of the long-term, fixed-rate debt (c) (106,592 ) Interest-rate swaps with future settlement dates expected to be amortized over the life of long-term debt (155,047 ) Accumulated other comprehensive loss at December 31, 2019 $ (233,520 ) (a) - All amounts are presented net of tax. (b) - Based on December 31, 2019, commodity prices, we will realize $28.9 million in net gains, net of tax, over the next 12 months and $0.8 million in net loss, net of tax, thereafter. (c) - Losses of $20.3 million , net of tax, will be reclassified into earnings during the next 12 months as the hedged items affect earnings. The remaining amounts in accumulated other comprehensive loss relate primarily to our retirement and other postretirement benefit plan obligations, which are expected to be amortized over the average remaining service period of employees participating in these plans. The following table sets forth the effect of reclassifications from accumulated other comprehensive loss to net income for the periods indicated: Details about Accumulated Other Comprehensive Loss Components Years Ended December 31, Affected Line Item in the Consolidated Statements of Income 2019 2018 2017 ( Thousands of dollars ) Risk-management assets/liabilities Commodity contracts $ 50,345 $ (29,596 ) $ (69,561 ) Commodity sales revenues/ cost of sales and fuel Interest-rate contracts (23,230 ) (18,287 ) (21,025 ) Interest expense 27,115 (47,883 ) (90,586 ) Income before income taxes (6,058 ) 11,013 26,899 Income taxes 21,057 (36,870 ) (63,687 ) Net income Noncontrolling interests — — (18,146 ) Less: Net income attributable noncontrolling interests $ 21,057 $ (36,870 ) $ (45,541 ) Net income attributable to ONEOK Retirement and other postretirement benefit plan obligations (a) Amortization of net loss $ (12,946 ) $ (18,398 ) $ (15,265 ) Other income (expense) Amortization of unrecognized prior service credit 227 1,662 1,662 Other income (expense) (12,719 ) (16,736 ) (13,603 ) Income before income taxes 2,925 3,849 5,441 Income taxes $ (9,794 ) $ (12,887 ) $ (8,162 ) Net income attributable to ONEOK Risk-management assets/liabilities of unconsolidated affiliates Interest-rate contracts $ (91 ) $ (36 ) $ (367 ) Equity in net earnings from investments 21 8 97 Income taxes (70 ) (28 ) (270 ) Net income Noncontrolling interests — — (106 ) Less: Net income attributable to noncontrolling interests $ (70 ) $ (28 ) $ (164 ) Net income attributable to ONEOK Total reclassifications for the period attributable to ONEOK $ 11,193 $ (49,785 ) $ (53,867 ) Net income attributable to ONEOK (a) - These components of accumulated other comprehensive loss are included in the computation of net periodic benefit cost. See Note K for additional detail of our net periodic benefit cost.

EARNINGS PER SHARE EARNINGS PER

EARNINGS PER SHARE EARNINGS PER SHARE (Notes)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share [Text Block]	EARNINGS PER SHARE The following tables set forth the computation of basic and diluted EPS for the periods indicated: Year Ended December 31, 2019 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 1,277,477 413,560 $ 3.09 Diluted EPS Effect of dilutive securities — 1,884 Net income available for common stock and common stock equivalents $ 1,277,477 415,444 $ 3.07 Year Ended December 31, 2018 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 1,150,603 411,485 $ 2.80 Diluted EPS Effect of dilutive securities — 2,710 Net income attributable to ONEOK available for common stock and common stock equivalents $ 1,150,603 414,195 $ 2.78 Year Ended December 31, 2017 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 387,074 297,477 $ 1.30 Diluted EPS Effect of dilutive securities — 2,303 Net income attributable to ONEOK available for common stock and common stock equivalents $ 387,074 299,780 $ 1.29

SHARE-BASED PAYMENTS SHARE-BASE

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Notes)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
SHARE-BASED PAYMENTS	SHARE-BASED PAYMENTS The ONEOK, Inc. Equity Compensation Plan (ECP) and the ONEOK, Inc. Long-Term Incentive Plan (LTIP) historically provided for the granting of stock-based compensation, including incentive stock options, nonstatutory stock options, stock bonus awards, restricted stock awards, restricted stock unit awards, performance stock awards and performance unit awards to eligible employees and the granting of stock awards to nonemployee directors. The ECP was terminated immediately following the issuance of new awards in February 2018. The awards issued prior to the termination remain subject to the terms of the ECP and the applicable award agreement. Similarly, the LTIP was terminated in May 2018, and the awards issued under the LTIP prior to the termination date remain subject to the terms of the LTIP and the applicable award agreement. In May 2018, our shareholders approved the ONEOK, Inc. Equity Incentive Plan (EIP), which has been used for all new equity awards since such date. We have reserved 8.5 million shares of common stock for issuance under the EIP and at December 31, 2019 , we had 7.6 million shares available for issuance under the plan. This calculation of available shares reflects shares issued and estimated shares expected to be issued upon vesting of outstanding awards granted under the EIP, excluding estimated forfeitures expected to be returned to the plan. Restricted Stock Units - We have granted restricted stock units to key employees that vest at the end of a three -year period and entitle the grantee to receive shares of our common stock. Restricted stock unit awards are measured at fair value as if they were vested and issued on the grant date and adjusted for estimated forfeitures. Restricted stock unit awards granted accrue dividend equivalents in the form of additional restricted stock units prior to vesting. Compensation expense is recognized on a straight-line basis over the vesting period of the award. Performance Unit Awards - We have granted performance unit awards to key employees that vest at the end of a three -year period. Upon vesting, a holder of outstanding performance units is entitled to receive a number of shares of our common stock equal to a percentage ( 0% to 200% ) of the performance units granted, based on our total shareholder return over the vesting period, compared with the total shareholder return of a peer group of other energy companies over the same period. Performance unit awards are measured at fair value on the grant date based on a Monte Carlo model and adjusted for estimated forfeitures. Performance stock unit awards granted accrue dividend equivalents in the form of additional performance units prior to vesting. Compensation expense is recognized on a straight-line basis over the vesting period of the award. Stock Compensation for Non-Employee Directors The ONEOK, Inc. Stock Compensation Plan for Non-Employee Directors (the DSCP) and the LTIP historically provided for the granting of nonstatutory stock options, stock bonus awards, including performance unit awards and restricted stock awards. The DSCP was terminated in May 2018 and replaced by the EIP. Under the EIP, awards may be granted by the Executive Compensation Committee at any time, until grants have been made for all shares authorized under the EIP. The maximum number of shares of common stock and cash-based awards that can be issued to a participant under the EIP during any year is limited to $0.8 million in value as of the grant date. No performance unit awards or restricted stock awards have been made to nonemployee directors under the EIP, LTIP or DSCP. There are no options outstanding under the EIP, LTIP or DSCP. General For all awards outstanding, we used a 3% forfeiture rate based on historical forfeitures under our share-based payment plans. We currently use treasury stock to satisfy our share-based payment obligations. Compensation expense for our share-based payment plans was $46.5 million , $33.2 million and $27.7 million during 2019, 2018 and 2017, respectively, before related tax benefits of $31.7 million , $12.2 million and $11.1 million , respectively. Restricted Stock Unit Activity As of December 31, 2019 , we had $15.4 million of total unrecognized compensation cost related to our nonvested restricted stock unit awards, which is expected to be recognized over a weighted-average period of 1.8 years . The following tables set forth activity and various statistics for our restricted stock unit awards: Number of Units Weighted Average Price Nonvested December 31, 2018 1,025,193 $ 34.68 Granted 262,399 $ 58.07 Released to participants (541,871 ) $ 19.73 Forfeited (46,731 ) $ 49.61 Nonvested December 31, 2019 698,990 $ 54.05 2019 2018 2017 Weighted-average grant date fair value (per share) $ 58.07 $ 46.94 $ 45.11 Fair value of units granted (thousands of dollars) $ 15,238 $ 13,907 $ 12,685 Grant date fair value of units vested (thousands of dollars) $ 10,691 $ 9,552 $ 7,258 Performance Unit Activity As of December 31, 2019 , we had $23.5 million of total unrecognized compensation cost related to the nonvested performance unit awards, which is expected to be recognized over a weighted-average period of 1.8 years . The following tables set forth activity and various statistics related to the performance unit awards and the assumptions used in the valuations at the respective grant dates: Number of Units Weighted Average Price Nonvested December 31, 2018 1,243,643 $ 44.08 Granted 338,427 $ 68.02 Released to participants (636,628 ) $ 23.59 Forfeited (7,621 ) $ 39.54 Nonvested December 31, 2019 937,821 $ 66.67 2019 2018 2017 Volatility (a) 27.10% 39.20% 40.59% Dividend yield 5.05% 5.49% 4.68% Risk-free interest rate 2.47% 2.44% 1.49% (a) - Volatility was based on historical volatility over three years using daily stock price observations. 2019 2018 2017 Weighted-average grant date fair value (per share) $ 68.02 $ 59.57 $ 56.65 Fair value of units granted (thousands of dollars) $ 23,020 $ 22,081 $ 17,621 Grant date fair value of units vested (thousands of dollars) $ 15,018 $ 12,545 $ 8,704 Employee Stock Purchase Plan We have reserved a total of 11.6 million shares of common stock for issuance under our ONEOK, Inc. Employee Stock Purchase Plan (the ESPP). Subject to certain exclusions, all employees are eligible to participate in the ESPP. Employees can choose to have up to 10% of their base pay withheld from each paycheck during the offering period to purchase our common stock, subject to terms and limitations of the plan. The purchase price of the stock is 85% of the lower of its grant date or exercise date market price. Approximately 62% , 60% and 58% of employees participated in the plan in 2019, 2018 and 2017, respectively. Under the plan, we sold 171,590 shares at $51.24 per share in 2019, 165,877 shares at $45.53 per share in 2018 and 151,803 shares at $44.20 per share in 2017. Employee Stock Award Program Under our Employee Stock Award Program, we issued, for no monetary consideration, to all eligible employees one share of our common stock when the per-share closing price of our common stock on the NYSE was for the first time at or above $13 per share, and one additional share of common stock when the per-share closing price of our common stock on the NYSE was at or above each one dollar increment above $13. The total number of shares of our common stock available for issuance under this program is 900,000 . Shares issued to employees under this program during 2019 and 2018 totaled 14,022 and 2,553 , respectively. Compensation expense related to the Employee Stock Award Program was $1.0 million and $0.2 million for 2019 and 2018, respectively. No shares were issued to employees under this program during 2017. As of the date of this report, the next award will be issued when our common stock closes at or above $78 . Deferred Compensation Plan for Non-Employee Directors The ONEOK, Inc. Deferred Compensation Plan for Non-Employee Directors provides our nonemployee directors the option to defer all or a portion of their compensation for their service on our Board of Directors. Under the plan, directors may elect either a cash deferral option or a phantom stock option. Under the cash deferral option, directors may elect to defer the receipt of all or a portion of their annual retainer fees, which will be credited with interest during the deferral period. Under the phantom stock option, directors may defer all or a portion of their annual retainer fees and receive such fees on a deferred basis in the form of shares of common stock under our EIP, which earn the equivalent of dividends declared on our common stock. Shares are distributed to nonemployee directors at the fair market value of our common stock at the date of distribution.

EMPLOYEE BENEFIT PLANS EMPLOYEE

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Notes)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
EMPLOYEE BENEFIT PLANS	EMPLOYEE BENEFIT PLANS Retirement and Other Postretirement Benefit Plans Retirement Plans - We have a defined benefit pension plan covering certain employees and former employees hired prior to January 1, 2005. Employees hired after December 31, 2004, and employees who accepted a one-time opportunity to opt out of our defined benefit pension plan historically were covered by our Profit Sharing Plan, which was merged into our 401(k) Plan as of December 31, 2018. In addition, we have a supplemental executive retirement plan for the benefit of certain officers. No new participants in our supplemental executive retirement plan have been approved since 2005, and effective January 2014, the plan was formally closed to new participants. We fund our retirement costs at a level needed to maintain or exceed the minimum funding levels required by the Employee Retirement Income Security Act of 1974, as amended, and the Pension Protection Act of 2006. Other Postretirement Benefit Plans - We sponsor health and welfare plans that provide postretirement medical and life insurance benefits to employees hired prior to 2017 who retire with at least five years of full-time service. The postretirement medical plan for pre-Medicare participants is contributory with retiree contributions adjusted periodically and contains other cost-sharing features such as deductibles and coinsurance. The postretirement medical plan for Medicare-eligible participants is an account-based plan under which participants may elect to purchase private insurance policies under a private exchange and/or seek reimbursement of other eligible medical expenses. Obligations and Funded Status - The following table sets forth our retirement and other postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 Change in benefit obligation ( Thousands of dollars ) Benefit obligation, beginning of period $ 466,994 $ 481,615 $ 46,840 $ 57,938 Service cost 7,825 7,339 468 845 Interest cost 20,528 17,659 2,038 2,108 Plan participants’ contributions — — 1,142 1,050 Actuarial loss (gain) 55,954 (24,345 ) 5,101 (10,233 ) Benefits paid (16,452 ) (15,274 ) (3,280 ) (4,868 ) Benefit obligation, end of period 534,849 466,994 52,309 46,840 Change in plan assets Fair value of plan assets, beginning of period 290,684 306,008 30,800 34,133 Actual return on plan assets 58,060 (12,350 ) 8,087 (998 ) Employer contributions 14,500 12,300 2,000 1,100 Plan participants’ contributions — — 1,142 1,050 Benefits paid (16,452 ) (15,274 ) (2,969 ) (4,485 ) Fair value of plan assets, end of period 346,792 290,684 39,060 30,800 Balance at December 31 $ (188,057 ) $ (176,310 ) $ (13,249 ) $ (16,040 ) Current liabilities $ (4,616 ) $ (4,514 ) $ — $ — Noncurrent liabilities (183,441 ) (171,796 ) (13,249 ) (16,040 ) Balance at December 31 $ (188,057 ) $ (176,310 ) $ (13,249 ) $ (16,040 ) The table above includes the supplemental executive retirement plan obligation. ONEOK has investments included in other assets on the Consolidated Balance Sheets, which totaled $98.9 million and $87.7 million at December 31, 2019 and 2018 , respectively, for the purpose of funding the obligation. These assets are not assets of the supplemental executive retirement plan and are excluded from the table above. The accumulated benefit obligation for our retirement plans was $498.8 million and $434.4 million at December 31, 2019 and 2018 , respectively. The actuarial gains and losses impacting our benefit obligations for our retirement and other postretirement benefit plans are due primarily to changes in the discount rate assumptions discussed in the “Actuarial Assumptions” section below. Components of Net Periodic Benefit Cost - The following table sets forth the components of net periodic benefit cost for our retirement and other postretirement benefit plans for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2019 2018 2017 2019 2018 2017 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 7,825 $ 7,339 $ 6,896 $ 468 $ 845 $ 662 Interest cost 20,528 17,659 18,645 2,038 2,108 2,261 Expected return on plan assets (23,600 ) (23,917 ) (21,376 ) (2,285 ) (2,690 ) (2,257 ) Amortization of prior service credit — — — (227 ) (1,662 ) (1,662 ) Amortization of net loss 12,649 17,060 13,586 297 1,338 1,679 Net periodic benefit cost $ 17,402 $ 18,141 $ 17,751 $ 291 $ (61 ) $ 683 Other Comprehensive Income (Loss) - The following table sets forth the amounts recognized in other comprehensive income (loss) related to our retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2019 2018 2017 2019 2018 2017 ( Thousands of dollars ) Net gain (loss) $ (25,389 ) $ (16,351 ) $ (16,572 ) $ 700 $ 6,545 $ (328 ) Prior service cost (601 ) — — — — — Amortization of prior service credit — — — (227 ) (1,662 ) (1,662 ) Amortization of net loss 12,649 17,060 13,586 297 1,338 1,679 Deferred income taxes (a) 3,068 (18,928 ) (960 ) (177 ) (2,831 ) 82 Total recognized in other comprehensive income (loss) $ (10,273 ) $ (18,219 ) $ (3,946 ) $ 593 $ 3,390 $ (229 ) (a) - Year ended December 31, 2018, includes the impact of adopting ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.” The table below sets forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit expense for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 ( Thousands of dollars ) Prior service credit (cost) $ (601 ) $ — $ — $ 227 Accumulated loss (172,952 ) (160,212 ) (4,110 ) (5,108 ) Accumulated other comprehensive loss (173,553 ) (160,212 ) (4,110 ) (4,881 ) Deferred income taxes 46,354 43,286 1,389 1,567 Accumulated other comprehensive loss, net of tax $ (127,199 ) $ (116,926 ) $ (2,721 ) $ (3,314 ) Actuarial Assumptions - The following table sets forth the weighted-average assumptions used to determine benefit obligations for retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 Discount rate 3.50% 4.50% 3.50% 4.50% Compensation increase rate 3.70% 3.65% NA NA The following table sets forth the weighted-average assumptions used to determine net periodic benefit costs for the periods indicated: Years Ended December 31, 2019 2018 2017 Discount rate - retirement plans 4.50% 3.75% 4.50% Discount rate - other postretirement plans 4.50% 3.75% 4.25% Expected long-term return on plan assets 7.50% 8.00% 7.75% Compensation increase rate 3.65% 3.00% 3.10% We determine our overall expected long-term rate of return on plan assets based on our review of historical returns and economic growth models. We determine our discount rates annually utilizing portfolios of high quality bonds matched to the estimated benefit cash flows of our retirement and other postretirement benefit plans. Bonds selected to be included in the portfolios are only those rated by S&P or Moody’s as an AA or Aa2 rating or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds. Health Care Cost Trend Rates - The following table sets forth the assumed health care cost-trend rates for the periods indicated: 2019 2018 Health care cost-trend rate assumed for next year 7.00% 6.50% Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate) 5.00% 5.00% Year that the rate reaches the ultimate trend rate 2024 2022 Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment policy for our defined benefit pension plan follows a glide path approach toward liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, real estate and hedge funds. The target allocation for the assets of our retirement plan as of December 31, 2019, is as follows: Domestic and international equities 42 % Long duration fixed income 30 % Return-seeking credit 11 % Hedge funds 10 % Real estate funds 7 % Total 100 % As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above. The following tables set forth the plan assets by fair value category as of the measurement date for our defined benefit pension and other postretirement benefit plans: Pension Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 47 $ — $ — $ 47 $ 149,985 $ 150,032 Real estate funds — — — — 23,885 23,885 Government obligations — — — — 50,708 50,708 Corporate obligations (b) — — — — 85,898 85,898 Common/collective trusts — 3,263 — 3,263 — 3,263 Cash 63 — — 63 — 63 Other investments (c) — — — — 32,943 32,943 Fair value of plan assets $ 110 $ 3,263 $ — $ 3,373 $ 343,419 $ 346,792 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category repre sen ts alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no u nfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Pension Benefits December 31, 2018 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 58 $ — $ — $ 58 $ 116,790 $ 116,848 Real estate funds — — — — 20,569 20,569 Government obligations — — — — 48,913 48,913 Corporate obligations (b) — — — — 69,377 69,377 Common/collective trusts — 3,961 — 3,961 — 3,961 Cash 95 — — 95 — 95 Other investments (c) — — — — 30,921 30,921 Fair value of plan assets $ 153 $ 3,961 $ — $ 4,114 $ 286,570 $ 290,684 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no unfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Other Postretirement Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) $ 2,043 $ — $ — $ 2,043 Money market funds — 2,428 — 2,428 Insurance and group annuity contracts — 34,589 — 34,589 Fair value of plan assets $ 2,043 $ 37,017 $ — $ 39,060 (a) - This category represents securities of the respective market sector from diverse industries. Other Postretirement Benefits December 31, 2018 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) $ 1,792 $ — $ — $ 1,792 Money market funds 1 413 — 414 Insurance and group annuity contracts — 28,594 — 28,594 Fair value of plan assets $ 1,793 $ 29,007 $ — $ 30,800 (a) - This category represents securities of the respective market sector from diverse industries. Contributions - During 2019 , we made $14.5 million in contributions to our defined benefit pension plan and $2.0 million in contributions to our other postretirement benefit plans. We contributed $12.1 million to our defined benefit pension plan in January 2020 and expect to make $2.0 million in contributions to our other postretirement plans in the remainder of 2020. Pension and Other Postretirement Benefit Payments - Benefit payments for our defined benefit pension and other postretirement benefit plans for the period ending December 31, 2019 , were $ 16.5 million and $ 3.3 million, respectively. The following table sets forth the defined benefit pension and other postretirement benefits payments expected to be paid in 2020 through 2029: Pension Benefits Other Postretirement Benefits Benefits to be paid in: ( Thousands of dollars ) 2020 $ 18,277 $ 3,422 2021 $ 19,252 $ 3,399 2022 $ 20,202 $ 3,519 2023 $ 21,170 $ 3,454 2024 $ 22,228 $ 3,446 2025 through 2029 $ 123,959 $ 16,385 The expected benefits to be paid are based on the same assumptions used to measure our benefit obligation at December 31, 2019 , and include estimated future employee service. Other Employee Benefit Plans 401(k) Plan - We have a 401(k) Plan covering all employees, and employee contributions are discretionary. We historically maintained a profit-sharing plan for all employees hired after December 31, 2004, which was merged into our 401(k) Plan as of December 31, 2018, and ceased to exist as a separate plan. We match 100% of employee 401(k) contributions up to 6% of each participant’s eligible compensation, subject to certain limits, and generally make a quarterly profit sharing contribution equal to 1% of each profit-sharing participant’s eligible compensation during the quarter and an annual discretionary profit-sharing contribution. Our contributions made to the plan, including profit-sharing contributions, were $30.4 million , $28 million and $21.1 million in 2019, 2018 and 2017 , respectively. Nonqualified Deferred Compensation Plan - The 2019 Nonqualified Deferred Compensation Plan and its predecessor nonqualified deferred compensation plans (collectively, the NQDC Plan) provide select employees, as approved by our Chief Executive Officer, with the option to defer portions of their compensation and provide nonqualified deferred compensation benefits that are not available due to limitations on employer and employee contributions to qualified defined contribution plans under the federal tax laws. The NQDC Plan also provides benefits in excess of applicable tax limits for certain participants in the defined benefit pension plan who are not participants in the supplemental executive retirement plan. Our contributions to the plan were not material in 2019, 2018 and 2017 .

INCOME TAXES (Notes)

INCOME TAXES (Notes)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The following table sets forth our provision for income taxes for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Current tax expense (benefit) Federal $ (1,278 ) $ 260 $ 295 State 963 1,633 1,670 Total current tax expense (benefit) (315 ) 1,893 1,965 Deferred tax expense Federal 327,806 319,551 376,728 State 44,923 41,459 68,589 Total deferred tax expense 372,729 361,010 445,317 Total provision for income taxes $ 372,414 $ 362,903 $ 447,282 The following table is a reconciliation of our income tax provision for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Income before income taxes $ 1,650,991 $ 1,517,935 $ 1,040,801 Less: Net income attributable to noncontrolling interests — 3,329 205,678 Net income attributable to ONEOK before income taxes 1,650,991 1,514,606 835,123 Federal statutory income tax rate 21.0 % 21.0 % 35.0 % Provision for federal income taxes 346,708 318,067 292,293 State income taxes, net of federal benefit 34,545 38,668 16,197 Deferred tax rate change, inclusive of valuation allowance 11,340 5,552 141,283 Excess tax benefits from share-based compensation (20,983 ) (4,644 ) — Other, net 804 5,260 (2,491 ) Income tax provision $ 372,414 $ 362,903 $ 447,282 The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated: December 31, December 31, Deferred tax assets ( Thousands of dollars ) Employee benefits and other accrued liabilities $ 99,510 $ 91,587 Federal net operating loss 858,030 420,318 State net operating loss and benefits 171,779 108,004 Derivative instruments 83,710 22,108 Other 12,769 13,378 Total deferred tax assets 1,225,798 655,395 Valuation allowance for state net operating loss and tax credits Carryforward expected to expire prior to utilization (94,794 ) (73,820 ) Net deferred tax assets 1,131,004 581,575 Deferred tax liabilities Excess of tax over book depreciation 84,631 73,113 Investment in partnerships (a) 1,582,436 728,193 Total deferred tax liabilities 1,667,067 801,306 Net deferred tax assets (liabilities) $ (536,063 ) $ (219,731 ) (a) Due primarily to excess of tax over book depreciation. In December 2017, the Tax Cuts and Jobs Act was signed into law. The Tax Cuts and Jobs Act made extensive changes to the U.S. tax laws and included provisions that, beginning in 2018, reduced the U.S. corporate tax rate to 21% from 35% , increased expensing for capital investment, limited the interest deduction, and limited the use of net operating losses to offset future taxable income. We revalued our deferred tax assets and liabilities as required at enactment. At that time, our net deferred tax assets represented expected corporate tax benefits in the future. The reduction in the federal corporate tax rate reduced these benefits, which resulted in a one-time noncash charge to net income through income tax expense of $141.3 million, inclusive of the valuation allowance described below, recorded in the fourth quarter 2017. Tax benefits related to certain state net operating loss, tax credit carryforwards and charitable contribution carryforwards will begin expiring in 2020. Due to the Tax Cuts and Jobs Act and the impact of increased expensing for capital investment, we believe that it is more likely than not that the tax benefits of certain carryforwards will not be utilized prior to their expirations; therefore, we recorded a valuation allowance of $11.3 million, $ 5.6 million and $ 54.1

UNCONSOLIDATED AFFILIATES (Note

UNCONSOLIDATED AFFILIATES (Notes)	12 Months Ended
	Dec. 31, 2019
Equity Method Investments and Joint Ventures [Abstract]
UNCONSOLIDATED AFFILIATES	UNCONSOLIDATED AFFILIATES Investments in Unconsolidated Affiliates - The following table sets forth our investments in unconsolidated affiliates for the periods indicated: Net Ownership Interest December 31, December 31, ( Thousands of dollars ) Northern Border Pipeline 50% $ 307,209 $ 381,623 Overland Pass Pipeline 50% 417,473 429,295 Roadrunner 50% 80,816 93,857 Other Various 56,346 64,375 Investments in unconsolidated affiliates (a) $ 861,844 $ 969,150 (a) - Equity-method goodwill (Note A ) was $38.8 million at December 31, 2019 and 2018 . Equity in Net Earnings from Investments and Impairments - The following table sets forth our equity in net earnings from investments for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Northern Border Pipeline $ 68,871 $ 67,854 $ 68,153 Overland Pass Pipeline 63,698 65,887 60,067 Roadrunner 26,839 22,993 19,150 Other (4,867 ) 1,649 11,908 Equity in net earnings from investments $ 154,541 $ 158,383 $ 159,278 Impairment of equity investments $ — $ — $ (4,270 ) Impairment Charges - In 2017, following a review of nonstrategic assets for potential divestiture, we recorded $4.3 million of noncash impairment charges related to a nonstrategic equity investment located in Oklahoma, which was later sold. Unconsolidated Affiliates Financial Information - The following tables set forth summarized combined financial information of our unconsolidated affiliates for the periods indicated: December 31, December 31, ( Thousands of dollars ) Balance Sheet Current assets $ 149,564 $ 158,723 Property, plant and equipment, net $ 2,314,631 $ 2,413,662 Other noncurrent assets $ 13,252 $ 16,273 Current liabilities $ 88,142 $ 83,057 Long-term debt $ 581,327 $ 480,731 Other noncurrent liabilities $ 76,685 $ 47,826 Accumulated other comprehensive income (loss) $ (28,373 ) $ 2,053 Owners’ equity $ 1,759,666 $ 1,974,991 Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Income Statement Revenues $ 634,135 $ 637,762 $ 639,102 Operating expenses $ 291,210 $ 276,373 $ 277,121 Net income $ 315,274 $ 337,694 $ 347,692 Distributions paid to us (a) $ 257,644 $ 197,285 $ 196,114 (a) As determined by the Northern Border Pipeline Management Committee, we received an additional distribution of $50.0 million from Northern Border Pipeline during the year ended December 31, 2019. We incurred expenses in transactions with unconsolidated affiliates of $164.7 million , $153.9 million and $156.1 million for 2019, 2018 and 2017 , respectively, primarily related to Overland Pass Pipeline and Northern Border Pipeline. Accounts payable to our equity-method investees at December 31, 2019 and 2018, were $13.5 million and $14.7 million , respectively. Northern Border Pipeline - The Northern Border Pipeline partnership agreement provides that distributions to Northern Border Pipeline’s partners are to be made on a pro rata basis according to each partner’s percentage interest. The Northern Border Pipeline Management Committee determines the amount and timing of such distributions. Any changes to, or suspension of, the cash distribution policy of Northern Border Pipeline requires the unanimous approval of the Northern Border Pipeline Management Committee. Cash distributions are equal to 100% of distributable cash flow as determined from Northern Border Pipeline’s financial statements based upon EBITDA less interest expense and maintenance capital expenditures. Loans or other advances from Northern Border Pipeline to its partners or affiliates are prohibited under its credit agreement. In 2019 and 2018, we made no contributions to Northern Border Pipeline. In 2017, we made equity contributions of $83 million to Northern Border Pipeline. Northern Border Pipeline entered into a settlement with shippers that was approved by the FERC in February 2018. The settlement provides for tiered rate reductions beginning January 1, 2018, that reduced tariff rates 12.5% by January 2020, compared with previous tariff rates and requires new rates to be established by January 2024. We do not expect the impact of lower tariff rates on Northern Border Pipeline’s earnings and cash distributions to be material to us. Overland Pass Pipeline - The Overland Pass Pipeline agreement provides that distributions to Overland Pass Pipeline’s members are to be made on a pro rata basis according to each member’s percentage interest. The Overland Pass Pipeline Company Management Committee determines the amount and timing of such distributions. Any changes to, or suspension of, the cash distributions from Overland Pass Pipeline requires the unanimous approval of the Overland Pass Pipeline Company Management Committee. Cash distributions are equal to 100% of available cash as defined in the limited liability company agreement. Roadrunner - The Roadrunner agreement provides that distributions to members are made on a pro rata basis according to each member’s ownership interest. As the operator, we have been delegated the authority to determine such distributions in accordance with, and on the frequency set forth in, the Roadrunner agreement. Cash distributions are equal to 100% of available cash, as defined in the limited liability company agreement. In 2019, 2018 and 2017, our contributions to Roadrunner were not material. We have an operating agreement with Roadrunner that provides for reimbursement or payment to us for management services and certain operating costs. Reimbursements and payments from Roadrunner included in operating income in our Consolidated Statements of Income for the years ended December 31, 2019 , 2018 and 2017, were not material.

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Notes)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Commitments - Firm transportation and storage contracts are fixed-price contracts that provide us with firm transportation and storage capacity. The following table sets forth our firm transportation and storage contract payments for the periods indicated: Firm Transportation and Storage Contracts ( Millions of dollars ) 2020 $ 61.6 2021 48.1 2022 40.1 2023 36.4 2024 34.3 Thereafter 177.9 Total $ 398.4 Environmental Matters and Pipeline Safety - The operation of pipelines, plants and other facilities for the gathering, processing, transportation and storage of natural gas, NGLs, condensate and other products is subject to numerous and complex laws and regulations pertaining to health, safety and the environment. As an owner and/or operator of these facilities, we must comply with laws and regulations that relate to air and water quality, hazardous and solid waste management and disposal, cultural resource protection and other environmental matters. The cost of planning, designing, constructing and operating pipelines, plants and other facilities must incorporate compliance with these laws and regulations and safety standards. Failure to comply with these laws and regulations may trigger a variety of administrative, civil and potentially criminal enforcement measures, including citizen suits, which can include the assessment of monetary penalties, the imposition of remedial requirements and the issuance of injunctions or restrictions on operation or construction. Management believes that, based on currently known information, compliance with these laws and regulations will not affect adversely our results of operations, financial condition or cash flows. Legal Proceedings - Gas Index Pricing Litigation - As previously reported, we and our affiliate, ONEOK Energy Services Company, L.P., along with several other energy companies, were named as defendants in multiple lawsuits arising from alleged market manipulation or false reporting of natural gas prices to natural gas-index publications alleged to have occurred prior to 2003. In September 2019, we settled Sinclair Oil Corporation v. ONEOK Energy Services Company, L.P. (filed in the United States District Court for the District of Wyoming) for an immaterial amount with cash on hand. This was the last remaining case arising from the Gas Index Pricing Litigation. Other Legal Proceedings - We are a party to various other litigation matters and claims that have arisen in the normal course of our operations. While the results of these litigation matters and claims cannot be predicted with certainty, we believe the reasonably possible losses from such matters, individually and in the aggregate, are not material. Additionally, we believe the probable final outcome of such matters will not affect adversely our consolidated results of operations, financial position or cash flows.

LEASES (Notes)

LEASES (Notes)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	O . LEASES Adoption of ASC Topic 842: Leases - We adopted Topic 842 using the modified retrospective method and the optional transition method to record the adoption impact through a cumulative-effect adjustment to retained earnings as of January 1, 2019. Results for reporting periods beginning after January 1, 2019, are presented under Topic 842, while prior periods are not adjusted and continue to be reported under the accounting standards in effect for those periods. Practical Expedients and Policies Elected - We applied the short-term policy election, which allows us to exclude from recognition leases with an initial term of 12 months or less. We elected the hindsight expedient, which allows us to use hindsight in assessing lease term; the package of practical expedients permitted under the guidance, which among other things, allows us to carry forward the historical lease classification; and the land easement expedient, which allows us to apply the guidance prospectively at adoption for land easements on existing agreements. Adoption - Adoption of Topic 842 resulted in new operating lease assets and lease liabilities on our Consolidated Balance Sheet of $17.5 million and $17.4 million , respectively, as of January 1, 2019. The difference between the lease assets and lease liabilities was recorded as an adjustment to the beginning balance of retained earnings, which represents the cumulative impact of adopting the standard. Our accounting for finance leases did not change. Adoption of Topic 842 did not materially impact our Consolidated Financial Statements. Leases - We lease certain buildings, warehouses, office space, pipeline capacity, land and equipment, including pipeline equipment, rail cars, and information technology equipment. Our lease payments are generally straight-line and the exercise of lease renewal options, which vary in term, is at our sole discretion. We include renewal periods in a lease term if we are reasonably certain to exercise available renewal options. Our lease agreements do not include any residual value guarantees or material restrictive covenants. Through ONEOK Leasing Company, L.L.C. and ONEOK Parking Company, L.L.C., we own an office building and a parking garage and lease excess space in these facilities to affiliates and others. Our consolidated lease income is not material. The following table sets forth supplemental information about our cash flows: Year Ended December 31, 2019 ( Thousands of dollars ) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 6,213 Financing cash flows for finance lease $ 1,764 Right-of-use assets obtained in exchange for operating lease liabilities (noncash) $ 4,097 The following table sets forth information about our lease assets and liabilities included in our Consolidated Balance Sheet for the period indicated: Leases Location in our Consolidated Balance Sheet December 31, 2019 ( Thousands of dollars ) Assets Operating leases Other assets $ 15,147 Finance lease Property, plant and equipment 28,286 Finance lease Accumulated depreciation (1,320 ) Total leased assets $ 42,113 Liabilities Current Operating leases Other current liabilities $ 1,883 Finance lease Finance lease liability 1,949 Noncurrent Operating leases Other deferred credits 13,509 Finance lease Finance lease liability 24,296 Total lease liabilities $ 41,637 The following table sets forth information about our leases for the period indicated: Year Ended December 31, 2019 At December 31, 2019 Location in our Consolidated Statement of Income Lease Cost Weighted-Average Remaining Lease Term Weighted-Average Discount Rate (a) ( Thousands of dollars ) ( Years ) Operating leases Operations and maintenance $ 6,803 10.4 4.58% Finance lease 8.8 10.00% Amortization of lease assets Depreciation and amortization 1,131 Interest on lease liabilities Interest expense 2,721 Total lease cost $ 10,655 (a) - Our weighted-average discount rates represent the rate implicit in the lease or our incremental borrowing rate for a term equal to the remaining term of the lease. The following table sets forth the maturity of our lease liabilities as of December 31, 2019: Finance Lease Operating Leases ( Millions of dollars ) 2020 $ 4.5 $ 2.5 2021 4.5 2.1 2022 4.5 2.0 2023 4.5 1.9 2024 4.5 1.9 2025 and beyond 17.1 9.2 Total lease payments 39.6 19.6 Less: Interest 13.4 4.2 Present value of lease liabilities $ 26.2 $ 15.4 Our future lease payments presented under the previous accounting standard as of December 31, 2018, are not materially different than those presented above. As of December 31, 2019, we have entered into an additional operating lease that had not yet commenced with an estimated present value of $75.6 million and a lease term of 10 years , which is excluded from our maturities table above and our lease right-of-use assets and liabilities.

REVENUES (Notes)

REVENUES (Notes)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customer [Text Block]	REVENUES Accounting Policies - See Note A for revenue recognition accounting policies. Contract Assets and Contract Liabilities - The following tables set forth the changes in our contract asset and contract liability balances for the periods indicated: Contract Assets ( Millions of dollars ) Balance at January 1, 2018 (a) $ 6.4 Amounts invoiced in excess of revenue recognized (0.9 ) Net additions 0.7 Balance at December 31, 2018 (b) 6.2 Amounts invoiced in excess of revenue recognized (1.7 ) Net additions 0.5 Balance at December 31, 2019 (c) $ 5.0 (a) - Balance includes $0.9 million of current assets. (b) - Contract assets of $1.7 million and $4.5 million are included in other current assets and other assets, respectively, in our Consolidated Balance Sheet. (c) - Contract assets of $1.3 million and $3.7 million are included in other current assets and other assets, respectively, in our Consolidated Balance Sheet. Contract Liabilities ( Millions of dollars ) Balance at January 1, 2018 (a) $ 33.3 Revenue recognized included in beginning balance (19.5 ) Net additions 17.9 Balance at December 31, 2018 (b) 31.7 Revenue recognized included in beginning balance (15.6 ) Net additions 41.0 Balance at December 31, 2019 (c) $ 57.1 (a) - Balance includes $19.5 million of current liabilities. (b) - Contract liabilities of $15.6 million and $16.1 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (c) - Contract liabilities of $22.2 million and $34.9 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. In 2019, net additions for contract liabilities relate primarily to deferred revenue on contributions in aid of construction received from customers and NGL storage contracts. Receivables from Customers and Revenue Disaggregation - Substantially all of the balances in accounts receivable on our Consolidated Balance Sheets at December 31, 2019, and December 31, 2018, relate to customer receivables. Revenues sources are disaggregated in Note Q. Practical Expedients - We do not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) variable consideration on contracts for which we recognize revenue at the amount to which we have the right to invoice for services performed. Transaction Price Allocated to Unsatisfied Performance Obligations - The following table presents aggregate value allocated to unsatisfied performance obligations as of December 31, 2019, and the amounts we expect to recognize in revenue in future periods, related primarily to firm transportation and storage contracts with remaining contract terms ranging from one month to 24 years : Expected Period of Recognition in Revenue ( Millions of dollars ) 2020 $ 343.5 2021 290.4 2022 214.8 2023 166.4 2024 and beyond 807.2 Total estimated transaction price allocated to unsatisfied performance obligations $ 1,822.3 The table above excludes variable consideration allocated entirely to wholly unsatisfied performance obligations, wholly unsatisfied promises to transfer distinct goods or services that are part of a single performance obligation and consideration we determine to be fully constrained. Information on the nature of the variable consideration excluded and the nature of the performance obligations to which the variable consideration relates can be found in the description of the major contract types discussed in Note A . The amounts we determined to be fully constrained relate to future sales obligations under long-term sales contracts where the transaction price is not known and minimum volume agreements, which we consider to be fully constrained until invoiced.

SEGMENTS (Notes)

SEGMENTS (Notes)	12 Months Ended
	Dec. 31, 2019
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
SEGMENTS	SEGMENTS Segment Descriptions - Our operations are divided into three reportable business segments, as follows: • our Natural Gas Gathering and Processing segment gathers, treats and processes natural gas; • our Natural Gas Liquids segment gathers, treats, fractionates and transports NGLs and stores, markets and distributes NGL products; and • our Natural Gas Pipelines segment operates regulated interstate and intrastate natural gas transmission pipelines and natural gas storage facilities. Other and eliminations consist of corporate costs, the operating and leasing activities of our headquarters building and related parking facility and eliminations necessary to reconcile our reportable segments to our Consolidated Financial Statements. Accounting Policies - The accounting policies of the segments are described in Note A . For each of the years ended December 31, 2019, 2018 and 2017 , we had no single customer from which we received 10% or more of our consolidated revenues. Operating Segment Information - The following tables set forth certain selected financial information for our operating segments for the periods indicated: Year Ended December 31, 2019 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) NGL and condensate sales $ 1,224,378 $ 7,910,833 $ — $ 9,135,211 Residue natural gas sales 966,149 — 1,244 967,393 Gathering, processing and exchange services revenue 164,299 414,238 — 578,537 Transportation and storage revenue — 197,483 466,266 663,749 Other 13,813 9,962 4,477 28,252 Total revenues (c) 2,368,639 8,532,516 471,987 11,373,142 Cost of sales and fuel (exclusive of depreciation and operating costs) (1,302,310 ) (6,690,918 ) (4,628 ) (7,997,856 ) Operating costs (368,352 ) (456,892 ) (157,230 ) (982,474 ) Equity in net earnings from investments (6,292 ) 65,123 95,710 154,541 Noncash compensation expense and other 10,965 15,936 2,977 29,878 Segment adjusted EBITDA $ 702,650 $ 1,465,765 $ 408,816 $ 2,577,231 Depreciation and amortization $ (219,519 ) $ (196,132 ) $ (57,250 ) $ (472,901 ) Investments in unconsolidated affiliates $ 34,426 $ 439,393 $ 388,025 $ 861,844 Total assets $ 6,795,744 $ 12,551,476 $ 2,094,072 $ 21,441,292 Capital expenditures $ 926,489 $ 2,796,604 $ 99,221 $ 3,822,314 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.4 billion , of which $1.2 billion related to sales within the segment, and cost of sales and fuel of $496.8 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $285.3 million and cost of sales and fuel of $20.0 million . (c) - Intersegment revenues for the Natural Gas Gathering and Processing segment totaled $1.2 billion . Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2019 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 9,135,211 $ (1,190,424 ) $ 7,944,787 Residue natural gas sales 967,393 (1,418 ) 965,975 Gathering, processing and exchange services revenue 578,537 — 578,537 Transportation and storage revenue 663,749 (15,646 ) 648,103 Other 28,252 (1,287 ) 26,965 Total revenues (a) $ 11,373,142 $ (1,208,775 ) $ 10,164,367 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (7,997,856 ) $ 1,209,816 $ (6,788,040 ) Operating costs $ (982,474 ) $ (390 ) $ (982,864 ) Depreciation and amortization $ (472,901 ) $ (3,634 ) $ (476,535 ) Equity in net earnings from investments $ 154,541 $ — $ 154,541 Investments in unconsolidated affiliates $ 861,844 $ — $ 861,844 Total assets $ 21,441,292 $ 370,829 $ 21,812,121 Capital expenditures $ 3,822,314 $ 26,035 $ 3,848,349 (a) - Noncustomer revenue for the year ended December 31, 2019, totaled $139.6 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2018 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) NGL and condensate sales $ 1,775,991 $ 10,319,847 $ — $ 12,095,838 Residue natural gas sales 1,084,162 — 9,772 1,093,934 Gathering, processing and exchange services revenue 163,194 404,897 — 568,091 Transportation and storage revenue — 199,018 414,969 613,987 Other 11,230 10,816 6,994 29,040 Total revenues (c) 3,034,577 10,934,578 431,735 14,400,890 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,041,448 ) (9,176,813 ) (15,984 ) (11,234,245 ) Operating costs (368,939 ) (394,115 ) (144,259 ) (907,313 ) Equity in net earnings from investments 410 67,126 90,847 158,383 Noncash compensation expense and other 7,007 9,829 3,912 20,748 Segment adjusted EBITDA $ 631,607 $ 1,440,605 $ 366,251 $ 2,438,463 Depreciation and amortization $ (196,090 ) $ (174,007 ) $ (55,118 ) $ (425,215 ) Investments in unconsolidated affiliates $ 42,630 $ 451,040 $ 475,480 $ 969,150 Total assets $ 6,078,473 $ 9,663,640 $ 2,131,669 $ 17,873,782 Capital expenditures $ 694,611 $ 1,306,341 $ 119,185 $ 2,120,137 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion , of which $1.1 billion related to sales within the segment, and cost of sales and fuel of $506.0 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $266.6 million and cost of sales and fuel of $26.0 million . (c) - Intersegment revenues for the Natural Gas Gathering and Processing segment totaled $1.8 billion . Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2018 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 12,095,838 $ (1,794,342 ) $ 10,301,496 Residue natural gas sales 1,093,934 (2,832 ) 1,091,102 Gathering, processing and exchange services revenue 568,091 (21 ) 568,070 Transportation and storage revenue 613,987 (10,550 ) 603,437 Other 29,040 51 29,091 Total revenues (a) $ 14,400,890 $ (1,807,694 ) $ 12,593,196 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,234,245 ) $ 1,811,537 $ (9,422,708 ) Operating costs $ (907,313 ) $ 245 $ (907,068 ) Depreciation and amortization $ (425,215 ) $ (3,342 ) $ (428,557 ) Equity in net earnings from investments $ 158,383 $ — $ 158,383 Investments in unconsolidated affiliates $ 969,150 $ — $ 969,150 Total assets $ 17,873,782 $ 357,889 $ 18,231,671 Capital expenditures $ 2,120,137 $ 21,338 $ 2,141,475 (a) - Noncustomer revenue for the year ended December 31, 2018, totaled $(16.2) million related primarily to losses from derivatives on commodity contracts. Year Ended December 31, 2017 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) Sales to unaffiliated customers $ 1,750,655 $ 10,009,576 $ 411,490 $ 12,171,721 Intersegment revenues 1,275,919 616,628 8,442 1,900,989 Total revenues 3,026,574 10,626,204 419,932 14,072,710 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,216,355 ) (9,176,494 ) (43,424 ) (11,436,273 ) Operating costs (307,376 ) (358,278 ) (125,308 ) (790,962 ) Equity in net earnings from investments 12,098 59,876 87,304 159,278 Other 3,531 3,631 1,314 8,476 Segment adjusted EBITDA $ 518,472 $ 1,154,939 $ 339,818 $ 2,013,229 Depreciation and amortization $ (184,923 ) $ (167,277 ) $ (51,025 ) $ (403,225 ) Impairment of long-lived assets and equity investments $ (20,240 ) $ — $ — $ (20,240 ) Investments in unconsolidated affiliates $ 55,841 $ 457,467 $ 489,848 $ 1,003,156 Total assets $ 5,495,163 $ 8,782,700 $ 2,055,020 $ 16,332,883 Capital expenditures $ 284,205 $ 114,267 $ 95,564 $ 494,036 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion , of which $1.0 billion related to sales within the segment, and cost of sales and fuel of $497.4 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $264.9 million and cost of sales and fuel of $44.0 million . Year Ended December 31, 2017 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated Sales to unaffiliated customers $ 12,171,721 $ 2,186 $ 12,173,907 Intersegment revenues 1,900,989 (1,900,989 ) — Total revenues $ 14,072,710 $ (1,898,803 ) $ 12,173,907 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,436,273 ) $ 1,898,228 $ (9,538,045 ) Operating costs $ (790,962 ) $ (31,748 ) $ (822,710 ) Depreciation and amortization $ (403,225 ) $ (3,110 ) $ (406,335 ) Impairment of long-lived assets and equity investments $ (20,240 ) $ — $ (20,240 ) Equity in net earnings from investments $ 159,278 $ — $ 159,278 Investments in unconsolidated affiliates $ 1,003,156 $ — $ 1,003,156 Total assets $ 16,332,883 $ 513,054 $ 16,845,937 Capital expenditures $ 494,036 $ 18,357 $ 512,393 Years Ended December 31, 2019 2018 2017 Reconciliation of net income to total segment adjusted EBITDA ( Thousands of dollars ) Net income $ 1,278,577 $ 1,155,032 $ 593,519 Add: Interest expense, net of capitalized interest 491,773 469,620 485,658 Depreciation and amortization 476,535 428,557 406,335 Income taxes 372,414 362,903 447,282 Impairment charges — — 20,240 Noncash compensation expense 26,699 37,954 13,421 Other corporate costs and noncash items (a) (68,767 ) (15,603 ) 46,774 Total segment adjusted EBITDA $ 2,577,231 $ 2,438,463 $ 2,013,229 (a) - The year ended December 31, 2019, includes higher equity AFUDC related to our capital-growth projects compared with 2018 and 2017. The year ended December 31, 2017, includes our April 2017 $20.0 million contribution of Series E Preferred Stock to the Foundation and costs related to the Merger Transaction of $30.0 million .

QUARTERLY FINANCIAL DATA (UNAUD

QUARTERLY FINANCIAL DATA (UNAUDITED) (Notes)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
QUARTERLY FINANCIAL DATA (UNAUDITED)	QUARTERLY FINANCIAL DATA (UNAUDITED) Year Ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter ( Thousands of dollars, except per share amounts ) Total revenues $ 2,779,958 $ 2,457,575 $ 2,263,228 $ 2,663,606 Operating income $ 468,742 $ 476,146 $ 482,151 $ 487,314 Net income $ 337,208 $ 311,963 $ 309,155 $ 320,251 Net income available to common shareholders $ 336,933 $ 311,688 $ 308,880 $ 319,976 Earnings per share total Basic $ 0.82 $ 0.75 $ 0.75 $ 0.77 Diluted $ 0.81 $ 0.75 $ 0.74 $ 0.77 Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter ( Thousands of dollars except per share amounts ) Total revenues $ 3,102,077 $ 2,960,529 $ 3,393,890 $ 3,136,700 Operating income $ 419,699 $ 448,366 $ 495,534 $ 471,865 Net income $ 266,049 $ 282,179 $ 313,916 $ 292,888 Net income available to common shareholders $ 264,233 $ 280,773 $ 312,984 $ 292,613 Earnings per share total Basic $ 0.65 $ 0.68 $ 0.76 $ 0.71 Diluted $ 0.64 $ 0.68 $ 0.75 $ 0.70

SUPPLEMENTAL CONDENSED CONSOLID

SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION (Notes)	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Supplemental Condensed Consolidating Financial Information	SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION ONEOK and ONEOK Partners are issuers of certain public debt securities. We, ONEOK Partners and the Intermediate Partnership have cross guarantees in place for the indebtedness of ONEOK and ONEOK Partners. The Intermediate Partnership holds all of ONEOK Partners’ interests and equity in its subsidiaries, as well as a 50% interest in Northern Border Pipeline. In lieu of providing separate financial statements for each subsidiary issuer and guarantor, we have included the accompanying condensed consolidating financial statements based on Rule 3-10 of the SEC’s Regulation S-X. We have presented each of the parent and subsidiary issuers in separate columns in this single set of condensed consolidating financial statements. For purposes of the following footnote: • we are referred to as “Parent Issuer and Guarantor”; • ONEOK Partners is referred to as “Subsidiary Issuer and Guarantor”; • the Intermediate Partnership is referred to as “Guarantor Subsidiary”; and • the “Non-Guarantor Subsidiaries” are all subsidiaries other than the Guarantor Subsidiary and Subsidiary Issuer and Guarantor. The following supplemental condensed consolidating financial information is presented on an equity-method basis reflecting the separate accounts of ONEOK, ONEOK Partners and the Intermediate Partnership, the combined accounts of the Non-Guarantor Subsidiaries, the combined consolidating adjustments and eliminations, and our consolidated amounts for the periods indicated. Condensed Consolidating Statements of Income Year Ended December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 8,916.1 $ — $ 8,916.1 Services — — — 1,250.4 (2.1 ) 1,248.3 Total revenues — — — 10,166.5 (2.1 ) 10,164.4 Cost of sales and fuel (exclusive of items shown separately below) — — — 6,788.0 — 6,788.0 Operating expenses — — — 1,461.5 (2.1 ) 1,459.4 (Gain) loss on sale of assets — — 2.7 (0.1 ) — 2.6 Operating income — — (2.7 ) 1,917.1 — 1,914.4 Equity in net earnings from investments 1,898.7 1,906.2 1,908.9 116.3 (5,675.6 ) 154.5 Other income (expense), net 34.4 305.7 308.3 42.1 (616.6 ) 73.9 Interest expense, net (287.4 ) (308.3 ) (308.3 ) (204.4 ) 616.6 (491.8 ) Income before income taxes 1,645.7 1,903.6 1,906.2 1,871.1 (5,675.6 ) 1,651.0 Income taxes (367.1 ) — — (5.3 ) — (372.4 ) Net income 1,278.6 1,903.6 1,906.2 1,865.8 (5,675.6 ) 1,278.6 Less: Preferred stock dividends 1.1 — — — — 1.1 Net income available to common shareholders $ 1,277.5 $ 1,903.6 $ 1,906.2 $ 1,865.8 $ (5,675.6 ) $ 1,277.5 Net income $ 1,278.6 $ 1,903.6 $ 1,906.2 $ 1,865.8 $ (5,675.6 ) $ 1,278.6 Other comprehensive income (loss), net of tax (183.8 ) (2.6 ) (20.9 ) (20.5 ) 42.0 (185.8 ) Comprehensive income $ 1,094.8 $ 1,901.0 $ 1,885.3 $ 1,845.3 $ (5,633.6 ) $ 1,092.8 Year Ended December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 11,395.6 $ — $ 11,395.6 Services — — — 1,199.7 (2.1 ) 1,197.6 Total revenues — — — 12,595.3 (2.1 ) 12,593.2 Cost of sales and fuel (exclusive of items shown separately below) — — — 9,422.7 — 9,422.7 Operating expenses (0.6 ) — — 1,338.3 (2.1 ) 1,335.6 Gain on sale of assets — — — (0.6 ) — (0.6 ) Operating income 0.6 — — 1,834.9 — 1,835.5 Equity in net earnings from investments 1,655.6 1,660.5 1,660.5 116.3 (4,934.5 ) 158.4 Other income (expense), net 29.6 315.1 315.1 (36.0 ) (630.2 ) (6.4 ) Interest expense, net (179.4 ) (315.1 ) (315.1 ) (290.2 ) 630.2 (469.6 ) Income before income taxes 1,506.4 1,660.5 1,660.5 1,625.0 (4,934.5 ) 1,517.9 Income taxes (354.7 ) — — (8.2 ) — (362.9 ) Net income 1,151.7 1,660.5 1,660.5 1,616.8 (4,934.5 ) 1,155.0 Less: Net income attributable to noncontrolling interests — — — 3.3 — 3.3 Net income attributable to ONEOK 1,151.7 1,660.5 1,660.5 1,613.5 (4,934.5 ) 1,151.7 Less: Preferred stock dividends 1.1 — — — — 1.1 Net income available to common shareholders $ 1,150.6 $ 1,660.5 $ 1,660.5 $ 1,613.5 $ (4,934.5 ) $ 1,150.6 Net income $ 1,151.7 $ 1,660.5 $ 1,660.5 $ 1,616.8 $ (4,934.5 ) $ 1,155.0 Other comprehensive income (loss), net of tax (39.5 ) 101.1 85.9 62.6 (171.7 ) 38.4 Comprehensive income 1,112.2 1,761.6 1,746.4 1,679.4 (5,106.2 ) 1,193.4 Less: Comprehensive income attributable to noncontrolling interests — — — 3.3 — 3.3 Comprehensive income attributable to ONEOK $ 1,112.2 $ 1,761.6 $ 1,746.4 $ 1,676.1 $ (5,106.2 ) $ 1,190.1 Year Ended December 31, 2017 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 9,862.7 $ — $ 9,862.7 Services — — — 2,313.2 (2.0 ) 2,311.2 Total revenues — — — 12,175.9 (2.0 ) 12,173.9 Cost of sales and fuel (exclusive of items shown separately below) — — — 9,538.0 — 9,538.0 Operating expenses 17.8 — 9.2 1,204.0 (2.0 ) 1,229.0 Impairment of long-lived assets — — — 16.0 — 16.0 Gain on sale of assets — — — (0.9 ) — (0.9 ) Operating income (17.8 ) — (9.2 ) 1,418.8 — 1,391.8 Equity in net earnings from investments 1,236.6 1,215.7 1,224.9 100.7 (3,618.6 ) 159.3 Impairment of equity investments — — — (4.3 ) — (4.3 ) Other income (expense), net (12.3 ) 353.1 353.1 (8.0 ) (706.2 ) (20.3 ) Interest expense, net (137.1 ) (353.1 ) (353.1 ) (348.6 ) 706.2 (485.7 ) Income before income taxes 1,069.4 1,215.7 1,215.7 1,158.6 (3,618.6 ) 1,040.8 Income taxes (480.2 ) — — 32.9 — (447.3 ) Net income 589.2 1,215.7 1,215.7 1,191.5 (3,618.6 ) 593.5 Less: Net income attributable to noncontrolling interests 201.4 — — 4.3 — 205.7 Net income attributable to ONEOK 387.8 1,215.7 1,215.7 1,187.2 (3,618.6 ) 387.8 Less: Preferred stock dividends 0.8 — — — — 0.8 Net income available to common shareholders $ 387.0 $ 1,215.7 $ 1,215.7 $ 1,187.2 $ (3,618.6 ) $ 387.0 Net income $ 589.2 $ 1,215.7 $ 1,215.7 $ 1,191.5 $ (3,618.6 ) $ 593.5 Other comprehensive income (loss), net of tax 17.4 13.2 27.9 34.5 (55.9 ) 37.1 Comprehensive income 606.6 1,228.9 1,243.6 1,226.0 (3,674.5 ) 630.6 Less: Comprehensive income attributable to noncontrolling interests 232.4 — — 4.3 — 236.7 Comprehensive income attributable to ONEOK $ 374.2 $ 1,228.9 $ 1,243.6 $ 1,221.7 $ (3,674.5 ) $ 393.9 Condensed Consolidating Balance Sheets December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total Assets ( Millions of dollars ) Current assets Cash and cash equivalents $ 21.0 $ — $ — $ — $ — $ 21.0 Accounts receivable, net — — — 835.1 — 835.1 Materials and supplies — — — 201.7 — 201.7 Natural gas and NGLs in storage — — — 304.9 — 304.9 Other current assets 12.4 — — 95.2 — 107.6 Total current assets 33.4 — — 1,436.9 — 1,470.3 Property, plant and equipment Property, plant and equipment 166.6 — — 21,884.9 — 22,051.5 Accumulated depreciation and amortization 99.5 — — 3,603.3 — 3,702.8 Net property, plant and equipment 67.1 — — 18,281.6 — 18,348.7 Investments and other assets Investments 6,732.6 4,101.4 11,466.3 769.9 (22,208.4 ) 861.8 Intercompany notes receivable 8,950.9 6,903.2 — — (15,854.1 ) — Other assets 139.9 — — 992.1 (0.7 ) 1,131.3 Total investments and other assets 15,823.4 11,004.6 11,466.3 1,762.0 (38,063.2 ) 1,993.1 Total assets $ 15,923.9 $ 11,004.6 $ 11,466.3 $ 21,480.5 $ (38,063.2 ) $ 21,812.1 Liabilities and equity Current liabilities Current maturities of long-term debt $ — $ — $ — $ 7.7 $ — $ 7.7 Short-term borrowings 220.0 — — — — 220.0 Accounts payable 23.8 — — 1,186.1 — 1,209.9 Other current liabilities 243.8 63.3 — 275.6 — 582.7 Total current liabilities 487.6 63.3 — 1,469.4 — 2,020.3 Intercompany payables — — 7,364.9 8,489.2 (15,854.1 ) — Long-term debt, excluding current maturities 8,421.1 4,045.1 — 13.5 — 12,479.7 Deferred credits and other liabilities Deferred income taxes 417.1 — — 119.7 (0.7 ) 536.1 Other deferred credits 372.1 — — 177.9 — 550.0 Total deferred credits and other liabilities 789.2 — — 297.6 (0.7 ) 1,086.1 Commitments and contingencies Equity 6,226.0 6,896.2 4,101.4 11,210.8 (22,208.4 ) 6,226.0 Total liabilities and equity $ 15,923.9 $ 11,004.6 $ 11,466.3 $ 21,480.5 $ (38,063.2 ) $ 21,812.1 December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total Assets ( Millions of dollars ) Current assets Cash and cash equivalents $ 12.0 $ — $ — $ — $ — $ 12.0 Accounts receivable, net — — — 819.0 — 819.0 Materials and supplies — — — 141.2 — 141.2 Natural gas and NGLs in storage — — — 296.7 — 296.7 Other current assets 29.1 — — 100.6 — 129.7 Total current assets 41.1 — — 1,357.5 — 1,398.6 Property, plant and equipment Property, plant and equipment 145.5 — — 17,885.5 — 18,031.0 Accumulated depreciation and amortization 92.0 — — 3,172.3 — 3,264.3 Net property, plant and equipment 53.5 — — 14,713.2 — 14,766.7 Investments and other assets Investments 6,153.5 3,548.1 9,721.6 791.1 (19,245.1 ) 969.2 Intercompany notes receivable 5,308.6 7,701.5 1,528.0 — (14,538.1 ) — Other assets 115.9 — — 982.3 (1.0 ) 1,097.2 Total investments and other assets 11,578.0 11,249.6 11,249.6 1,773.4 (33,784.2 ) 2,066.4 Total assets $ 11,672.6 $ 11,249.6 $ 11,249.6 $ 17,844.1 $ (33,784.2 ) $ 18,231.7 Liabilities and equity Current liabilities Current maturities of long-term debt $ — $ 500.0 $ — $ 7.7 $ — $ 507.7 Accounts payable 31.3 — — 1,085.0 — 1,116.3 Other current liabilities 123.2 81.0 — 280.2 — 484.4 Total current liabilities 154.5 581.0 — 1,372.9 — 2,108.4 Intercompany payables — — 7,701.5 6,836.6 (14,538.1 ) — Long-term debt, excluding current maturities 4,510.7 4,341.4 — 21.2 — 8,873.3 Deferred credits and other liabilities Deferred income taxes 112.3 — — 108.4 (1.0 ) 219.7 Other deferred credits 315.6 — — 135.2 — 450.8 Total deferred credits and other liabilities 427.9 — — 243.6 (1.0 ) 670.5 Commitments and contingencies Equity 6,579.5 6,327.2 3,548.1 9,369.8 (19,245.1 ) 6,579.5 Total liabilities and equity $ 11,672.6 $ 11,249.6 $ 11,249.6 $ 17,844.1 $ (33,784.2 ) $ 18,231.7 Condensed Consolidating Statements of Cash Flows Year Ended December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 1,010.1 $ 1,332.9 $ 68.9 $ 2,198.9 $ (2,664.0 ) $ 1,946.8 Investing activities Capital expenditures (25.6 ) — — (3,822.7 ) — (3,848.3 ) Other investing activities — — 74.6 4.9 — 79.5 Cash provided by (used in) investing activities (25.6 ) — 74.6 (3,817.8 ) — (3,768.8 ) Financing activities Dividends paid (1,457.6 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (1,457.6 ) Intercompany borrowings (advances), net (3,618.6 ) 801.8 1,188.5 1,628.3 — — Short-term borrowings, net 220.0 — — — — 220.0 Issuance of long-term debt, net of discounts 4,185.4 — — — — 4,185.4 Repayment of long-term debt (249.6 ) (800.0 ) — (7.7 ) — (1,057.3 ) Issuance of common stock 29.0 — — — — 29.0 Other, net (84.1 ) (2.7 ) — (1.7 ) — (88.5 ) Cash provided by (used in) financing activities (975.5 ) (1,332.9 ) (143.5 ) 1,618.9 2,664.0 1,831.0 Change in cash and cash equivalents 9.0 — — — — 9.0 Cash and cash equivalents at beginning of period 12.0 — — — — 12.0 Cash and cash equivalents at end of period $ 21.0 $ — $ — $ — $ — $ 21.0 Year Ended December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 1,325.1 $ 1,344.7 $ 67.9 $ 2,113.0 $ (2,664.0 ) $ 2,186.7 Investing activities Capital expenditures (18.8 ) — — (2,122.7 ) — (2,141.5 ) Other investing activities — — 15.3 11.3 — 26.6 Cash provided by (used in) investing activities (18.8 ) — 15.3 (2,111.4 ) — (2,114.9 ) Financing activities Dividends paid (1,335.1 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (1,335.1 ) Distributions to noncontrolling interests — — — (3.5 ) — (3.5 ) Intercompany borrowings (advances), net (2,154.4 ) 912.3 1,248.8 (6.7 ) — — Repayment of short-term borrowings, net (614.7 ) — — — — (614.7 ) Issuance of long-term debt, net of discounts 1,795.8 — — — — 1,795.8 Repayment of long-term debt — (925.0 ) — (7.7 ) — (932.7 ) Issuance of common stock 1,204.0 — — — — 1,204.0 Acquisition of noncontrolling interests (195.0 ) — — — — (195.0 ) Other, net (32.1 ) — — 16.3 — (15.8 ) Cash used in financing activities (1,331.5 ) (1,344.7 ) (83.2 ) (1.6 ) 2,664.0 (97.0 ) Change in cash and cash equivalents (25.2 ) — — — — (25.2 ) Cash and cash equivalents at beginning of period 37.2 — — — — 37.2 Cash and cash equivalents at end of period $ 12.0 $ — $ — $ — $ — $ 12.0 Year Ended December 31, 2017 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 947.4 $ 1,348.3 $ 59.0 $ 1,353.7 $ (2,393.0 ) $ 1,315.4 Investing activities Capital expenditures — — — (512.4 ) — (512.4 ) Contributions to unconsolidated affiliates — — (83.0 ) (4.9 ) — (87.9 ) Other investing activities — — 14.8 17.9 — 32.7 Cash used in investing activities — — (68.2 ) (499.4 ) — (567.6 ) Financing activities Dividends paid (829.4 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (829.4 ) Distributions to noncontrolling interests — — — (5.3 ) (271.0 ) (276.3 ) Intercompany borrowings (advances), net (2,500.7 ) 2,001.2 1,340.8 (841.3 ) — — Borrowing (repayment) of short-term borrowings, net 614.7 (1,110.3 ) — — — (495.6 ) Issuance of long-term debt, net of discounts 1,190.5 — — — — 1,190.5 Repayment of long-term debt (87.1 ) (900.0 ) — (7.7 ) — (994.8 ) Issuance of common stock 471.4 — — — — 471.4 Other, net (18.1 ) (7.2 ) — — — (25.3 ) Cash provided by (used in) financing activities (1,158.7 ) (1,348.3 ) 8.8 (854.3 ) 2,393.0 (959.5 ) Change in cash and cash equivalents (211.3 ) — (0.4 ) — — (211.7 ) Cash and cash equivalents at beginning of period 248.5 — 0.4 — — 248.9 Cash and cash equivalents at end of period $ 37.2 $ — $ — $ — $ — $ 37.2

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Consolidation	Consolidation - Our Consolidated Financial Statements include our accounts and the accounts of our subsidiaries over which we have control or are the primary beneficiary. All intercompany balances and transactions have been eliminated in consolidation. Investments in unconsolidated affiliates are accounted for using the equity method if we have the ability to exercise significant influence over operating and financial policies of our investee. Under this method, an investment is carried at its acquisition cost and adjusted each period for contributions made, distributions received and our share of the investee’s comprehensive income. For the investments we account for under the equity method, the premium or excess cost over underlying fair value of net assets is referred to as equity-method goodwill. Impairment of equity investments is recorded when the impairments are other than temporary. These amounts are recorded as investments in unconsolidated affiliates on our accompanying Consolidated Balance Sheets. See Note M for disclosures of our unconsolidated affiliates. Distributions paid to us from our unconsolidated affiliates are classified as operating activities on our Consolidated Statements of Cash Flows until the cumulative distributions exceed our proportionate share of income from the unconsolidated affiliate since the date of our initial investment. The amount of cumulative distributions paid to us that exceeds our cumulative proportionate share of income in each period represents a return of investment and is classified as an investing activity on our Consolidated Statements of Cash Flows.
Use of Estimates	Use of Estimates - The preparation of our Consolidated Financial Statements and related disclosures in accordance with GAAP requires us to make estimates and assumptions with respect to values or conditions that cannot be known with certainty that affect the reported amounts on our Consolidated Financial Statements. Items that may be estimated include, but are not limited to, the economic useful life of assets, fair value of assets, liabilities and equity-method investments, obligations under employee benefit plans, provisions for uncollectible accounts receivable, expenses for services received but for which no invoice has been received, provision for income taxes, including any deferred tax valuation allowances, the results of litigation and various other recorded or disclosed amounts. In addition, a portion of our revenues and cost of sales and fuel are recorded based on current month prices and estimated volumes. The estimates are reversed in the following month and recorded with actual volumes and prices. We evaluate our estimates on an ongoing basis using historical experience, consultation with experts and other methods we consider reasonable based on the particular circumstances. Nevertheless, actual results may differ significantly from the estimates. Any effects on our financial position or results of operations from revisions to these estimates are recorded in the period when the facts that give rise to the revision become known.
Fair Value Measurements	Fair Value Measurements - For our fair value measurements, we utilize market prices, third-party pricing services, present value methods and standard option valuation models to determine the price we would receive from the sale of an asset or the transfer of a liability in an orderly transaction at the measurement date. We measure the fair value of a group of financial assets and liabilities consistent with how a market participant would price the net risk exposure at the measurement date. Many of the contracts in our derivative portfolio are executed in liquid markets where price transparency exists. Our financial commodity derivatives are generally settled through a NYMEX or Intercontinental Exchange (ICE) clearing broker account with daily margin requirements. We validate our valuation inputs with third-party information and settlement prices from other sources, where available. We compute the fair value of our derivative portfolio by discounting the projected future cash flows from our derivative assets and liabilities to present value using interest-rate yields to calculate present-value discount factors derived from the implied forward LIBOR yield curve. The fair value of our forward-starting interest-rate swaps are determined using financial models that incorporate the implied forward LIBOR yield curve for the same period as the future interest-rate swap settlements. We consider current market data in evaluating counterparties’, as well as our own, nonperformance risk, net of collateral, by using counterparty-specific bond yields. Although we use our best estimates to determine the fair value of the derivative contracts we have executed, the ultimate market prices realized could differ materially from our estimates. Fair Value Hierarchy - At each balance sheet date, we utilize a fair value hierarchy to classify fair value amounts recognized or disclosed in our financial statements based on the observability of inputs used to estimate such fair value. The levels of the hierarchy are described below: • Level 1 - fair value measurements are based on unadjusted quoted prices for identical securities in active markets. These balances are composed predominantly of exchange-traded derivative contracts for natural gas and crude oil. • Level 2 - fair value measurements are based on significant observable pricing inputs, including quoted prices for similar assets and liabilities in active markets and inputs from third-party pricing services supported with corroborative evidence. These balances are composed of over-the-counter interest-rate derivatives. • Level 3 - fair value measurements are based on inputs that may include one or more unobservable inputs, including internally developed commodity price curves that incorporate market data from broker quotes and third-party pricing services. These balances are composed predominantly of exchange-cleared and over-the-counter derivatives to hedge NGL price risk and natural gas basis risk between various transaction locations and the NYMEX Henry Hub. Our commodity derivatives are generally valued using forward quotes provided by third-party pricing services that are validated with other market data. We believe any measurement uncertainty at December 31, 2019, is immaterial as our Level 3 fair value measurements are based on unadjusted pricing information from broker quotes and third-party pricing services. We do not believe that our Level 3 fair value estimates have a material impact on our results of operations, as our derivatives are accounted for as hedges. Determining the appropriate classification of our fair value measurements within the fair value hierarchy requires management’s judgment regarding the degree to which market data is observable or corroborated by observable market data. We categorize derivatives for which fair value is determined using multiple inputs within a single level, based on the lowest level input that is significant to the fair value measurement in its entirety. See Note B for our fair value measurements disclosures.
Cash and Cash Equivalents	Cash and Cash Equivalents - Cash equivalents consist of highly liquid investments, which are readily convertible into cash and have original maturities of three months or less.
Revenue from Contract with Customer [Policy Text Block]	Revenue Recognition - Revenues are recognized when control of the promised goods or services is transferred to our customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those goods or services. Our payment terms vary by customer and contract type, including requiring payment before products or services are delivered to certain customers. However, the term between customer prepayments, completion of our performance obligations, invoicing and receipt of payment due is not significant. A significant portion of supply volumes in our Natural Gas Gathering and Processing and Natural Gas Liquids segments are under contracts that include the purchase of commodities. Therefore, upon adoption of Topic 606, the contractual fees we charge on these contracts are considered a reduction of the commodity purchase price in cost of sales and fuel. In 2017 and prior periods, we recorded these fees as services revenue. See “Cost of Sales and Fuel” below for a description of these arrangements. Performance Obligations and Revenue Sources - Revenues sources are disaggregated in Note Q and are derived from commodity sales and services revenues, as described below: Commodity Sales (all segments) - We contract to deliver residue natural gas, condensate, unfractionated NGLs and/or NGL products to customers at a specified delivery point. Our sales agreements may be daily or longer-term contracts for a specified volume. We consider the sale and delivery of each unit of a commodity an individual performance obligation as the customer is expected to control, accept and benefit from each unit individually. We record revenue when the commodity is delivered to the customer as this represents the point in time when control of the product is transferred to the customer. Revenue is recorded based on the contracted selling price, which is generally index-based and settled monthly. Services Gathering only contracts ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we charge fees for providing midstream services, which include gathering and treating our customer’s natural gas. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. POP with fee contracts with producer take-in-kind rights ( Natural Gas Gathering and Processing segment ) - Under this type of contract, we do not control the stream of unprocessed natural gas that we receive at the wellhead due to the producer’s take-in-kind rights. We purchase a portion of the raw natural gas stream, charge fees for providing midstream services, which include gathering, treating, compressing and processing our customer’s natural gas. After performing these services, we return primarily the residue natural gas to the producer, sell the remaining commodities and remit a portion of the commodity sales proceeds to the producer less our contractual fees. Our performance obligation begins with delivery of raw natural gas to our system. This service is treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. Transportation and exchange contracts ( Natural Gas Liquids segment ) - Under this type of contract, we charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs. Our performance obligation begins with delivery of unfractionated NGLs or NGL products to our system. These services represent a series of distinct services that are treated as one performance obligation that is satisfied over time. We use the output method based on delivery of product to our system as the measure of progress, as our services are performed simultaneously. For transportation services under a tariff on our NGL transportation pipelines, fees are recorded upon redelivery to our customer at the completion of the transportation services. Storage contracts ( Natural Gas Liquids and Natural Gas Pipelines segments ) - We reserve a stated storage capacity and inject/withdraw/store commodities for our customer. The capacity reservation and injection/withdrawal/storage services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue as invoiced to our customers. For contracts that do not include a capacity reservation, transportation, injection and withdrawal fees are recognized in revenue as those services are provided and are dependent on the volume transported, injected or withdrawn by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Firm service transportation contracts ( Natural Gas Pipelines segment ) - We reserve a stated transportation capacity and transport commodities for our customer. The capacity reservation and transportation services are considered a bundled service, as we integrate them into one stand-ready obligation provided on a daily basis over the life of the agreement and satisfied over time. Fixed capacity reservation fees are allocated and evenly recognized in revenue. Capacity reservation fees that vary based on a stated or implied economic index and correspond with the costs to provide our services are recognized in revenue based on a daily effective fee rate. If the capacity reservation fees vary solely as a contract feature, contract assets or liabilities are recorded for the difference between the amount recorded in revenue and the amount billed to the customer. Transportation fees are recognized in revenue as those services are provided and are dependent on the volume transported by our customer, which is at our customer’s discretion. We use the output method based on the passage of time to measure satisfaction of the performance obligation associated with our daily stand-ready services. Interruptible transportation contracts ( Natural Gas Pipelines segment ) - We agree to transport natural gas on our pipelines between the customer’s specified nomination and delivery points if capacity is available after satisfying firm transportation service obligations. The transaction price is based on the transportation fees times the volumes transported. These fees may change over time based on an index or other factors provided in the agreement. We use the output method based on delivery of product to the customer to measure satisfaction of the performance obligation. The total consideration for delivered volumes is recorded in revenue at the time of delivery, when the customer obtains control. See Note P for our revenue disclosures. Contract Assets and Contract Liabilities - Contract assets and contract liabilities are recorded when the amount of revenue recognized from a contract with a customer differs from the amount billed to the customer and recorded in accounts receivable. Our contract asset balances at the beginning and end of the period primarily relate to our firm service transportation contracts with tiered rates. Our contract liabilities primarily represent deferred revenue on contributions in aid of construction received from customers for which revenue is recognized over the contract periods, which range from 5 to 10 years
Cost of Sales and Fuel	Cost of Sales and Fuel - Cost of sales and fuel primarily includes (i) the cost of purchased commodities, including NGLs, natural gas and condensate, (ii) fees incurred for third-party transportation, fractionation and storage of commodities, (iii) fuel and power costs incurred to operate our own facilities that gather, process, transport and store commodities, and (iv) an offset from the contractual fees deducted from the cost of purchased commodities under the contract types below: POP with fee contracts with no producer take-in-kind rights (Natural Gas Gathering and Processing segment ) - We purchase raw natural gas and charge contractual fees for providing midstream services, which include gathering, treating, compressing and processing the producer’s natural gas. After performing these services, we sell the commodities and return a portion of the commodity sales proceeds to the producer less our contractual fees. Purchase with fee ( Natural Gas Liquids segment ) - Under this type of contract, we purchase raw, unfractionated NGLs at an index price and charge fees for providing midstream services, which may include a bundled combination of gathering, transporting and/or fractionation of our customer’s NGLs.
Operations and Maintenance	Operations and Maintenance - Operations and maintenance primarily includes (i) payroll and benefit costs, (ii) third-party costs for operations, maintenance and integrity management, regulatory compliance and environmental and safety, and (iii) other business related service costs.
Accounts Receivable	Accounts Receivable - Accounts receivable represent valid claims against nonaffiliated customers for products sold or services rendered, net of allowances for doubtful accounts. We assess the creditworthiness of our counterparties on an ongoing basis and require security, including prepayments and other forms of collateral, when appropriate. Outstanding customer receivables are reviewed regularly for possible nonpayment indicators, and allowances for doubtful accounts are recorded based upon management’s estimate of collectability at each balance sheet date. At December 31, 2019 and 2018 , our allowance for doubtful accounts was not material. Update - Upon adoption of ASU 2016-13 in January 2020, we are required to present accounts receivable net of an allowance for credit losses to reflect the net amount expected to be collected. This assessment is based on historical information, current conditions and supportable forecasts. See “Recently Issued Accounting Standards Update” table below for more information.
Inventory	Inventory - The values of current natural gas and NGLs in storage are determined using the lower of weighted-average cost or net realizable value. Noncurrent natural gas and NGLs are classified as property and valued at cost. Materials and supplies are valued at average cost.
Commodity Imbalances	Commodity Imbalances - Commodity imbalances represent amounts payable or receivable for NGL exchange contracts and natural gas pipeline imbalances and are valued at market prices. Under the majority of our NGL exchange agreements, we physically receive volumes of unfractionated NGLs, including the risk of loss and legal title to such volumes, from the exchange counterparty. In turn, we deliver NGL products back to the customer and charge them gathering, transportation and fractionation fees. To the extent that the volumes we receive under such agreements differ from those we deliver, we record a net exchange receivable or payable position with the counterparties. These net exchange receivables and payables are generally settled with movements of NGL products rather than with cash. Natural gas pipeline imbalances are settled in cash or in-kind, subject to the terms of the pipelines’ tariffs or by agreement.
Derivatives and Risk Management	Derivatives and Risk Management - We utilize derivatives to reduce our market-risk exposure to commodity price and interest-rate fluctuations and to achieve more predictable cash flows. We record all derivative instruments at fair value, with the exception of normal purchases and normal sales transactions that are expected to result in physical delivery. Commodity price and interest-rate volatility may have a significant impact on the fair value of derivative instruments as of a given date. The accounting for changes in the fair value of a derivative instrument depends on whether it has been designated and qualifies as part of a hedging relationship and, if so, the reason for holding it. The table below summarizes the various ways in which we account for our derivative instruments and the impact on our Consolidated Financial Statements: Recognition and Measurement Accounting Treatment Balance Sheet Income Statement Normal purchases and normal sales - Fair value not recorded - Change in fair value not recognized in earnings Mark-to-market - Recorded at fair value - Change in fair value recognized in earnings Cash flow hedge - The gain or loss on the derivative instrument is reported initially as a component of accumulated other comprehensive income (loss) - The gain or loss on the derivative instrument is reclassified out of accumulated other comprehensive income (loss) into earnings when the forecasted transaction affects earnings Fair value hedge - Recorded at fair value - The gain or loss on the derivative instrument is recognized in earnings - Change in fair value of the hedged item is recorded as an adjustment to book value - Change in fair value of the hedged item is recognized in earnings To reduce our exposure to fluctuations in natural gas, NGLs and condensate prices, we periodically enter into futures, forward purchases and sales, options or swap transactions in order to hedge anticipated purchases and sales of natural gas, NGLs and condensate. Interest-rate swaps are used from time to time to manage interest-rate risk. Under certain conditions, we designate our derivative instruments as a hedge of exposure to changes in fair values or cash flows. We formally document all relationships between hedging instruments and hedged items, as well as risk-management objectives and strategies for undertaking various hedge transactions, and methods for assessing and testing correlation and hedge effectiveness. We specifically identify the forecasted transaction that has been designated as the hedged item in a cash flow hedge relationship. We assess the effectiveness of hedging relationships at inception of the hedge by performing an effectiveness analysis on our fair value and cash flow hedging relationships to determine whether the hedge relationships are highly effective. Subsequently we perform qualitative assessments. We also document our normal purchases and normal sales transactions that we expect to result in physical delivery and that we elect to exempt from derivative accounting treatment. The realized revenues and purchase costs of our derivative instruments not considered held for trading purposes and derivatives that qualify as normal purchases or normal sales that are expected to result in physical delivery are reported on a gross basis. Cash flows from futures, forwards, options and swaps that are accounted for as hedges are included in the same category as the cash flows from the related hedged items in our Consolidated Statements of Cash Flows. See Notes B and C for disclosures of our fair value measurements and risk-management and hedging activities.
Property, Plant and Equipment	Property, Plant and Equipment - Our properties are stated at cost, including AFUDC and capitalized interest. In some cases, the cost of regulated property retired or sold, plus removal costs, less salvage, is charged to accumulated depreciation. Gains and losses from sales or transfers of nonregulated properties or an entire operating unit or system of our regulated properties are recognized in income. Maintenance and repairs are charged directly to expense. The interest portion of AFUDC and capitalized interest represent the cost of borrowed funds used to finance construction activities for regulated and nonregulated projects, respectively. We capitalize interest costs during the construction or upgrade of qualifying assets. These costs are recorded as a reduction to interest expense. The equity portion of AFUDC represents the capitalization of the estimated average cost of equity used during the construction of major projects and is recorded in the cost of our regulated properties and as a credit to the allowance for equity funds used during construction. Our properties are depreciated using the straight-line method over their estimated useful lives. Generally, we apply composite depreciation rates to functional groups of property having similar economic circumstances. We periodically conduct depreciation studies to assess the economic lives of our assets. For our regulated assets, these depreciation studies are completed as a part of our rate proceedings or tariff filings, and the changes in economic lives, if applicable, are implemented prospectively when the new rates are approved. For our nonregulated assets, if it is determined that the estimated economic life changes, the changes are made prospectively. Changes in the estimated economic lives of our property, plant and equipment could have a material effect on our financial position or results of operations. Property, plant and equipment on our Consolidated Balance Sheets includes construction work in process for capital projects that have not yet been placed in service and therefore are not being depreciated. Assets are transferred out of construction work in process when they are substantially complete and ready for their intended use. See Note D for our property, plant and equipment disclosures.
Impairment of Goodwill and Long-Lived Assets, including Intangible Assets	Impairment of Goodwill and Long-Lived Assets, Including Intangible Assets - We assess our goodwill for impairment at least annually on July 1, unless events or changes in circumstances indicate an impairment may have occurred before that time. Our qualitative goodwill impairment analysis performed as of July 1, 2019, did not result in an impairment charge nor did our analysis reflect any reporting units at risk, and subsequent to that date, no event has occurred indicating that the implied fair value of each of our reporting units is less than the carrying value of its net assets. As part of our goodwill impairment test, we may first assess qualitative factors (including macroeconomic conditions, industry and market considerations, cost factors and overall financial performance) to determine whether it is more likely than not that the fair value of each of our reporting units is less than its carrying amount. If further testing is necessary or a quantitative test is elected, we perform a two-step impairment test for goodwill. In the first step, an initial assessment is made by comparing the fair value of a reporting unit with its book value, including goodwill. If the fair value is less than the book value, an impairment is indicated, and we must perform a second test to measure the amount of the impairment. In the second test, we calculate the implied fair value of the goodwill by deducting the fair value of all tangible and intangible net assets of the reporting unit from the fair value determined in step one of the assessment. If the carrying value of the goodwill exceeds the implied fair value of the goodwill, we will record an impairment charge. Update - Upon adoption of ASU 2017-04 in January 2020, the requirement to calculate the implied fair value of goodwill under the two-step impairment test was eliminated. See “Recently Issued Accounting Standards Update” table below for more information. To estimate the fair value of our reporting units, we use two generally accepted valuation approaches, an income approach and a market approach, using assumptions consistent with a market participant’s perspective. Under the income approach, we use anticipated cash flows over a period of years plus a terminal value and discount these amounts to their present value using appropriate discount rates. Under the market approach, we apply EBITDA multiples to forecasted EBITDA. The multiples used are consistent with historical asset transactions. The forecasted cash flows are based on average forecasted cash flows for a reporting unit over a period of years. We assess our long-lived assets for impairment whenever events or changes in circumstances indicate that an asset’s carrying amount may not be recoverable. An impairment is indicated if the carrying amount of a long-lived asset exceeds the sum of the undiscounted future cash flows expected to result from the use and eventual disposition of the asset. If an impairment is indicated, we record an impairment loss equal to the difference between the carrying value and the fair value of the long-lived asset. For the investments we account for under the equity method, the impairment test considers whether the fair value of the equity investment as a whole, not the underlying net assets, has declined and whether that decline is other than temporary. Therefore, we periodically evaluate the amount at which we carry our equity-method investments to determine whether current events or circumstances warrant adjustments to our carrying values. See Notes D , E and M for our long-lived assets, goodwill and intangible assets and investments in unconsolidated affiliates disclosures.
Regulation	Regulation - Depending on the specific service provided, our natural gas transmission pipelines, NGL pipelines and certain natural gas storage facilities are subject to rate regulation and/or accounting requirements by one or more of the FERC, OCC, KCC and RRC. Accordingly, portions of our Natural Gas Liquids and Natural Gas Pipelines segments follow the accounting and reporting guidance for regulated operations. In our Consolidated Financial Statements and our Notes to Consolidated Financial Statements, regulated operations are defined pursuant to Financial Accounting Standards Board’s (FASB) ASC 980, Regulated Operations. During the rate-making process for certain of our assets, regulatory authorities set the framework for what we can charge customers for our services and establish the manner that our costs are accounted for, including allowing us to defer recognition of certain costs and permitting recovery of the amounts through rates over time as opposed to expensing such costs as incurred. Certain examples of types of regulatory guidance include costs for fuel and losses, acquisition costs, contributions in aid of construction, charges for depreciation, and gains or losses on disposition of assets. This allows us to stabilize rates over time rather than passing such costs on to the customer for immediate recovery. Actions by regulatory authorities could have an effect on the amounts we may charge our customers. Any difference in the amount recoverable and the amount deferred is recorded as income or expense at the time of the regulatory action. A write-off of regulatory assets and costs not recovered may be required if all or a portion of the regulated operations have rates that are no longer (i) established by independent, third-party regulators and (ii) set at levels that will recover our costs when considering the demand and competition for our services.
Retirement and Other Postretirement Employee Benefits	Retirement and Other Postretirement Employee Benefits - We have defined benefit retirement plans covering certain employees and former employees. We sponsor welfare plans that provide postretirement medical and life insurance benefits to certain employees hired prior to 2017 who retire with at least five years of service. The expense and liability related to these plans is calculated using statistical and other factors that attempt to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, mortality and employment length. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in changes in the costs and liabilities we recognize. See Note K for our retirement and other postretirement employee benefits disclosures. We determine our overall expected long-term rate of return on plan assets based on our review of historical returns and economic growth models. We determine our discount rates annually utilizing portfolios of high quality bonds matched to the estimated benefit cash flows of our retirement and other postretirement benefit plans. Bonds selected to be included in the portfolios are only those rated by S&P or Moody’s as an AA or Aa2 rating or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.
Income Taxes	Income Taxes - Deferred income taxes are provided for the difference between the financial statement and income tax basis of assets and liabilities and carryforward items based on income tax laws and rates existing at the time the temporary differences are expected to reverse. Generally, the effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date of the rate change. We utilize a more-likely-than-not recognition threshold and measurement attribute for the financial statement recognition and measurement of a tax position that is taken or expected to be taken in a tax return. We reflect penalties and interest as part of income tax expense as they become applicable for tax provisions that do not meet the more-likely-than-not recognition threshold and measurement attribute. During 2019, 2018 and 2017 , we had no uncertain tax positions that required the establishment of a material reserve. We utilize the “with-and-without” approach for intra-period tax allocation for purposes of allocating total tax expense (or benefit) for the year among the various financial statement components. We file numerous consolidated and separate income tax returns with federal tax authorities of the United States along with the tax authorities of several states. We are not under any United States federal audits or statute waivers at this time. See Note L for our income taxes disclosures.
Asset Retirement Obligations	Asset Retirement Obligations - Asset retirement obligations represent legal obligations associated with the retirement of long-lived assets that result from the acquisition, construction, development and/or normal use of the asset. Certain of our natural gas gathering and processing, NGL and natural gas pipeline facilities are subject to agreements or regulations that give rise to our asset retirement obligations for removal or other disposition costs associated with retiring the assets in place upon the discontinued use of the assets. We recognize the fair value of a liability for an asset retirement obligation in the period when it is incurred if a reasonable estimate of the fair value can be made. We are not able to estimate reasonably the fair value of the asset retirement obligations for portions of our assets, primarily certain pipeline assets, because the settlement dates are indeterminable given our expected continued use of the assets with proper maintenance. We expect our pipeline assets, for which we are unable to estimate reasonably the fair value of the asset retirement obligation, will continue in operation as long as supply and demand for natural gas and NGLs exist. Based on the widespread use of natural gas for heating and cooking activities for residential users and electric-power generation for commercial users, as well as use of NGLs by the petrochemical industry, we expect supply and demand to exist for the foreseeable future. For our assets that we are able to make an estimate, the fair value of the liability is added to the carrying amount of the associated asset, and this additional carrying amount is depreciated over the life of the asset. The liability is accreted at the end of each period through charges to operating expense. If the obligation is settled for an amount other than the carrying amount of the liability, we will recognize a gain or loss on settlement. The depreciation and accretion expense are immaterial to our Consolidated Financial Statements.
Contingencies	Contingencies - Our accounting for contingencies covers a variety of business activities, including contingencies for legal and environmental exposures. We accrue these contingencies when our assessments indicate that it is probable that a liability has been incurred or an asset will not be recovered and an amount can be estimated reasonably. We expense legal fees as incurred and base our legal liability estimates on currently available facts and our estimates of the ultimate outcome or resolution. Accruals for estimated losses from environmental remediation obligations generally are recognized no later than completion of a remediation feasibility study. Recoveries of environmental remediation costs from other parties are recorded as assets when their receipt is deemed probable. Our expenditures for environmental evaluation, mitigation, remediation and compliance to date have not been significant in relation to our financial position or results of operations, and our expenditures related to environmental matters had no material effect on earnings or cash flows during 2019, 2018 and 2017 . Actual results may differ from our estimates resulting in an impact, positive or negative, on earnings. See Note N for additional discussion of contingencies.
Share-Based Payments	Share-Based Payments - We expense the fair value of share-based payments net of estimated forfeitures. We estimate forfeiture rates based on historical forfeitures under our share-based payment plans. See Note J for our share-based payments disclosures.
Earnings per Common Share	Earnings per Common Share - Basic EPS is calculated based on the daily weighted-average number of shares of common stock outstanding during the period, vested restricted and performance units that have been deferred and share awards deferred under the compensation plan for nonemployee directors. Diluted EPS is calculated based on the daily weighted-average number of shares of common stock outstanding during the period plus potentially dilutive components. The dilutive components are calculated based on the dilutive effect for each quarter. For fiscal-year periods, the dilutive components for each quarter are averaged to arrive at the fiscal year-to-date dilutive component. See Note I for our earnings per share disclosures.
Segment Reporting, Policy [Policy Text Block]	Segment Reporting - Our chief operating decision-maker reviews the financial performance of each of our three segments, as well as our financial performance as a whole, on a regular basis. Adjusted EBITDA by segment is utilized in this evaluation. We believe this financial measure is useful to investors because it and similar measures are used by many companies in our industry as a measurement of financial performance and are commonly employed by financial analysts and others to evaluate our financial performance and to compare financial performance among companies in our industry. Adjusted EBITDA for each segment is defined as net income adjusted for interest expense, depreciation and amortization, noncash impairment charges, income taxes, allowance for equity funds used during construction, noncash compensation expense, and other noncash items. This calculation may not be comparable with similarly titled measures of other companies. See Note Q for our segments disclosures. Accounting Policies - The accounting policies of the segments are described in Note A
New Accounting Pronouncements	The following tables provide a brief description of recent accounting pronouncements and our analysis of the effects on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standards that were adopted as of December 31, 2019 ASU 2016-02, “Leases (Topic 842)” The standard requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous GAAP. It also requires qualitative disclosures along with specific quantitative disclosures by lessees and lessors to meet the objective of enabling users of financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. First quarter 2019 We adopted this standard on January 1, 2019, using the modified retrospective method and the optional transition method to record the adoption impact through a cumulative adjustment to equity. On January 1, 2019, we recorded an immaterial cumulative effect for the adoption of the new standard and recorded $17.5 million of right-of-use assets and $17.4 million of lease liabilities related to operating leases that were not previously recorded on our Consolidated Balance Sheets. Our finance lease assets and liabilities at January 1, 2019, of $28.1 million and $28.0 million, respectively, did not change as a result of adopting this standard. See Note O for additional disclosures. ASU 2018-07, “Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting” The standard aligns the measurement and classification guidance for share-based payments to nonemployees with the guidance for share-based payments to employees, with certain exceptions. First quarter 2019 The impact of adopting this standard was not material. Standards that are not yet adopted as of December 31, 2019 ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments” The standard requires a financial asset (or a group of financial assets) measured at amortized cost basis to be presented net of the allowance for credit losses to reflect the net carrying value at the amount expected to be collected on the financial asset; and the initial allowance for credit losses for purchased financial assets, including available-for-sale debt securities, to be added to the purchase price rather than being reported as a credit loss expense. First quarter 2020 We adopted this standard in January 2020, and the impact of adopting this standard was not material. ASU 2017-04, “Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment” The standard simplifies the subsequent measurement of goodwill by eliminating the requirement to calculate the implied fair value of goodwill under step 2. Instead, an entity will recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value. The standard does not change step zero or step 1 assessments. First quarter 2020 We adopted this standard in January 2020, and the impact of adopting this standard was not material. ASU 2019-12, “Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes” The standard simplifies certain concepts in Topic 740, Income Taxes. First quarter 2021 We do not expect the adoption of this standard to materially impact us.

DEBT DEBT (Policies)

DEBT DEBT (Policies)	12 Months Ended
	Dec. 31, 2019
Debt Instrument [Line Items]
Debt Policy	We amortize premiums, discounts and expenses incurred in connection with the issuance of long-term debt consistent with the terms of the respective debt instrument.

EMPLOYEE BENEFIT PLANS EMPLOY_2

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Policies)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Investment, Policy [Policy Text Block]	Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment policy for our defined benefit pension plan follows a glide path approach toward liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, real estate and hedge funds. The target allocation for the assets of our retirement plan as of December 31, 2019, is as follows: Domestic and international equities 42 % Long duration fixed income 30 % Return-seeking credit 11 % Hedge funds 10 % Real estate funds 7 % Total 100 % As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	Retirement and Other Postretirement Employee Benefits - We have defined benefit retirement plans covering certain employees and former employees. We sponsor welfare plans that provide postretirement medical and life insurance benefits to certain employees hired prior to 2017 who retire with at least five years of service. The expense and liability related to these plans is calculated using statistical and other factors that attempt to anticipate future events. These factors include assumptions about the discount rate, expected return on plan assets, rate of future compensation increases, mortality and employment length. In determining the projected benefit obligations and costs, assumptions can change from period to period and may result in changes in the costs and liabilities we recognize. See Note K for our retirement and other postretirement employee benefits disclosures. We determine our overall expected long-term rate of return on plan assets based on our review of historical returns and economic growth models. We determine our discount rates annually utilizing portfolios of high quality bonds matched to the estimated benefit cash flows of our retirement and other postretirement benefit plans. Bonds selected to be included in the portfolios are only those rated by S&P or Moody’s as an AA or Aa2 rating or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds.

LEASES (Policies)

LEASES (Policies)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lessee, Leases [Policy Text Block]	Leases - We lease certain buildings, warehouses, office space, pipeline capacity, land and equipment, including pipeline equipment, rail cars, and information technology equipment. Our lease payments are generally straight-line and the exercise of lease renewal options, which vary in term, is at our sole discretion. We include renewal periods in a lease term if we are reasonably certain to exercise available renewal options. Our lease agreements do not include any residual value guarantees or material restrictive covenants. (a) - Our weighted-average discount rates represent the rate implicit in the lease or our incremental borrowing rate for a term equal to the remaining term of the lease.

SEGMENTS SEGMENTS (Policies)

SEGMENTS SEGMENTS (Policies)	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract] [Abstract]
Segment Reporting, Policy [Policy Text Block]	Segment Reporting - Our chief operating decision-maker reviews the financial performance of each of our three segments, as well as our financial performance as a whole, on a regular basis. Adjusted EBITDA by segment is utilized in this evaluation. We believe this financial measure is useful to investors because it and similar measures are used by many companies in our industry as a measurement of financial performance and are commonly employed by financial analysts and others to evaluate our financial performance and to compare financial performance among companies in our industry. Adjusted EBITDA for each segment is defined as net income adjusted for interest expense, depreciation and amortization, noncash impairment charges, income taxes, allowance for equity funds used during construction, noncash compensation expense, and other noncash items. This calculation may not be comparable with similarly titled measures of other companies. See Note Q for our segments disclosures. Accounting Policies - The accounting policies of the segments are described in Note A

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Recurring Fair Value Measurements	Recurring Fair Value Measurements - The following tables set forth our recurring fair value measurements for the periods indicated: December 31, 2019 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,892 $ — $ 55,557 $ 66,449 $ (28,588 ) $ 37,861 Interest-rate contracts — 581 — 581 — 581 Total derivative assets $ 10,892 $ 581 $ 55,557 $ 67,030 $ (28,588 ) $ 38,442 Derivative liabilities Commodity contracts Financial contracts $ (4,811 ) $ — $ (24,785 ) $ (29,596 ) $ 28,588 $ (1,008 ) Interest-rate contracts — (201,941 ) — (201,941 ) — (201,941 ) Total derivative liabilities $ (4,811 ) $ (201,941 ) $ (24,785 ) $ (231,537 ) $ 28,588 $ (202,949 ) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2019 , we held no cash and posted $8.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet. December 31, 2018 Level 1 Level 2 Level 3 Total - Gross Netting (a) Total - Net ( Thousands of dollars ) Derivative assets Commodity contracts Financial contracts $ 10,812 $ — $ 69,165 $ 79,977 $ (32,739 ) $ 47,238 Physical contracts — — 1,142 1,142 — 1,142 Interest-rate contracts — 19,005 — 19,005 — 19,005 Total derivative assets $ 10,812 $ 19,005 $ 70,307 $ 100,124 $ (32,739 ) $ 67,385 Derivative liabilities Commodity contracts Financial contracts $ (2,916 ) $ — $ (29,823 ) $ (32,739 ) $ 32,739 $ — Interest-rate contracts — (99,260 ) — (99,260 ) — (99,260 ) Total derivative liabilities $ (2,916 ) $ (99,260 ) $ (29,823 ) $ (131,999 ) $ 32,739 $ (99,260 ) (a) - Derivative assets and liabilities are presented in our Consolidated Balance Sheet on a net basis. We net derivative assets and liabilities when a legally enforceable master-netting arrangement exists between the counterparty to a derivative contract and us. At December 31, 2018 , we held no cash and posted $0.8 million of cash with various counterparties, which is included in other current assets in our Consolidated Balance Sheet.
Reconciliation of Level 3 Fair Value Measurements	The following table sets forth a reconciliation of our Level 3 fair value measurements for the periods indicated: Years Ended December 31, Derivative Assets (Liabilities) 2019 2018 ( Thousands of dollars ) Net assets (liabilities) at beginning of period $ 40,484 $ (32,838 ) Total changes in fair value: Gains (losses) included in net income (a) — (140 ) Settlements included in net income (a) (40,344 ) 29,141 New Level 3 derivatives included in other comprehensive income (loss) (b) 30,627 37,106 Unrealized change included in other comprehensive income (loss) (b) 5 7,215 Net assets (liabilities) at end of period $ 30,772 $ 40,484 (a) - Included in commodity sales revenues/cost of sales and fuel in our Consolidated Statements of Income. (b) - Included in change in fair value of derivatives in our Consolidated Statements of Comprehensive Income.

RISK MANAGEMENT AND HEDGING A_2

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES (Tables)	12 Months Ended
	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair Value of Derivatives	Fair Values of Derivative Instruments - All derivatives measured at fair value at December 31, 2019 and 2018, were designated as hedging instruments. See Note B for a discussion of the inputs associated with our fair value measurements. The following table sets forth the fair values of our derivative instruments presented on a gross basis for the periods indicated: December 31, 2019 December 31, 2018 Location in our Consolidated Balance Sheets Assets (Liabilities) Assets (Liabilities) ( Thousands of dollars ) Derivatives designated as hedging instruments Commodity contracts (a) Financial contracts Other current assets $ 64,858 $ (26,997 ) $ 78,891 $ (31,793 ) Other assets/other deferred credits 1,591 (2,599 ) 1,086 (946 ) Physical contracts Other current assets — — 1,142 — Interest-rate contracts Other current assets/other current liabilities — (90,161 ) 19,005 (15,012 ) Other assets/other deferred credits 581 (111,780 ) — (84,248 ) Total derivatives designated as hedging instruments $ 67,030 $ (231,537 ) $ 100,124 $ (131,999 )
Notional Amounts of Derivative Instruments	Notional Quantities for Derivative Instruments - The following table sets forth the notional quantities for derivative instruments held for the periods indicated: December 31, 2019 December 31, 2018 Contract Type Purchased/ Payor Sold/ Receiver Purchased/ Payor Sold/ Receiver Derivatives designated as hedging instruments: Cash flow hedges Fixed price -Natural gas ( Bcf ) Futures and swaps — (59.0 ) — (29.9 ) -Crude oil and NGLs ( MMBbl ) Futures, forwards and swaps 7.9 (17.4 ) 6.5 (13.8 ) Basis -Natural gas ( Bcf ) Futures and swaps — (59.0 ) — (29.9 ) Interest-rate contracts ( Billions of dollars ) Swaps $ 3.1 $ — $ 4.3 $ —
Schedule of Cash Flow Hedging Instruments Effect on Comprehensive Income (Loss)	The following table sets forth the unrealized change in fair value of cash flow hedges in other comprehensive income (loss) for the periods indicated: Derivatives in Cash Flow Hedging Relationships Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Commodity contracts $ 38,819 $ 53,217 $ (40,577 ) Interest-rate contracts (230,771 ) (60,584 ) 163 Total unrealized change in fair value of cash flow hedges in other comprehensive income (loss) $ (191,952 ) $ (7,367 ) $ (40,414 )
Schedule of Cash Flow Hedging Instruments Effect on Income	The following table sets forth the effect of cash flow hedges on net income for the periods indicated: Derivatives in Cash Flow Hedging Relationships Location of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Net Income Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Commodity contracts Commodity sales revenues/cost of sales and fuel $ 50,345 $ (29,596 ) $ (69,561 ) Interest-rate contracts Interest expense (23,230 ) (18,287 ) (21,025 ) Total change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income on derivatives $ 27,115 $ (47,883 ) $ (90,586 )

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment by Property Type	The following table sets forth our property, plant and equipment by property type, for the periods indicated: Estimated Useful Lives (Years) December 31, December 31, ( Thousands of dollars ) Nonregulated Gathering pipelines and related equipment 5 to 40 $ 4,316,936 $ 3,851,043 Processing and fractionation and related equipment 3 to 40 4,439,332 4,171,072 Storage and related equipment 3 to 54 684,635 656,455 Transmission pipelines and related equipment 5 to 54 797,678 782,258 General plant and other 2 to 60 610,013 547,424 Construction work in process — 1,645,663 797,182 Regulated Storage and related equipment 5 to 25 9,180 8,987 Natural gas transmission pipelines and related equipment 5 to 77 1,552,546 1,475,789 NGL transmission pipelines and related equipment 5 to 88 6,126,056 4,677,599 General plant and other 2 to 50 66,507 61,136 Construction work in process — 1,802,946 1,002,018 Property, plant and equipment 22,051,492 18,030,963 Accumulated depreciation and amortization - nonregulated (2,471,649 ) (2,168,855 ) Accumulated depreciation and amortization - regulated (1,231,158 ) (1,095,457 ) Net property, plant and equipment $ 18,348,685 $ 14,766,651
Average Depreciation Rates for Regulated Property	The average depreciation rates for our regulated property are set forth, by segment, in the following table for the periods indicated: Years Ended December 31, 2019 2018 2017 Natural Gas Liquids 2.0% 1.9% 1.9% Natural Gas Pipelines 2.1% 2.1% 2.1%

GOODWILL AND INTANGIBLE ASSET_2

GOODWILL AND INTANGIBLE ASSETS (Tables)	12 Months Ended
	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by Segment	The following table sets forth our goodwill, by segment, for the periods indicated: December 31, December 31, ( Thousands of dollars ) Natural Gas Gathering and Processing $ 153,404 $ 153,404 Natural Gas Liquids 371,217 371,217 Natural Gas Pipelines 156,375 156,479 Total goodwill $ 680,996 $ 681,100
Gross Carrying Amount and Accumulated Amortization of Intangible Assets	The following table reflects the gross carrying amount and accumulated amortization of intangible assets for the periods presented: December 31, December 31, ( Thousands of dollars ) Gross intangible assets $ 414,345 $ 411,650 Accumulated amortization (137,508 ) (125,608 ) Net intangible assets $ 276,837 $ 286,042

DEBT (Tables)

DEBT (Tables)	12 Months Ended
	Dec. 31, 2019
Long-term Debt, Unclassified [Abstract]
Debt	The following table sets forth our consolidated debt for the periods indicated: December 31, December 31, (Thousands of dollars) Commercial paper outstanding, bearing a weighted-average interest rate of 2.16% as of December 31, 2019 $ 220,000 $ — Senior unsecured obligations: $500,000 at 8.625% due March 2019 — 500,000 $300,000 at 3.8% due March 2020 — 300,000 $1,500,000 term loan, rate of 2.70% and 3.63% as of December 31, 2019 and 2018, respectively, due November 2021 1,250,000 550,000 $700,000 at 4.25% due February 2022 547,397 547,397 $900,000 at 3.375 % due October 2022 900,000 900,000 $425,000 at 5.0 % due September 2023 425,000 425,000 $500,000 at 7.5% due September 2023 500,000 500,000 $500,000 at 2.75% due September 2024 500,000 — $500,000 at 4.9 % due March 2025 500,000 500,000 $500,000 at 4.0% due July 2027 500,000 500,000 $800,000 at 4.55% due July 2028 800,000 800,000 $100,000 at 6.875% due September 2028 100,000 100,000 $700,000 at 4.35% due March 2029 700,000 — $750,000 at 3.4% due September 2029 750,000 — $400,000 at 6.0% due June 2035 400,000 400,000 $600,000 at 6.65% due October 2036 600,000 600,000 $600,000 at 6.85% due October 2037 600,000 600,000 $650,000 at 6.125% due February 2041 650,000 650,000 $400,000 at 6.2% due September 2043 400,000 400,000 $700,000 at 4.95% due July 2047 700,000 700,000 $1,000,000 at 5.2% due July 2048 1,000,000 450,000 $750,000 at 4.45% due September 2049 750,000 — Guardian Pipeline Weighted average 7.85% due December 2022 21,307 28,957 Total debt 12,813,704 9,451,354 Unamortized portion of terminated swaps 15,032 16,750 Unamortized debt issuance costs and discounts (121,329 ) (87,120 ) Current maturities of long-term debt (7,650 ) (507,650 ) Short-term borrowings (a) (220,000 ) — Long-term debt $ 12,479,757 $ 8,873,334 (a) - Individual issuances of commercial paper under our commercial paper program generally mature in 90 days or less.
Aggregate maturities of long-term debt outstanding	The aggregate maturities of long-term debt outstanding as of December 31, 2019, for the years 2020 through 2024 are shown below: Senior Unsecured Obligations Guardian Pipeline Total (Millions of dollars) 2020 $ — $ 7.7 $ 7.7 2021 $ 1,250.0 $ 7.7 $ 1,257.7 2022 $ 1,447.4 $ 5.9 $ 1,453.3 2023 $ 925.0 $ — $ 925.0 2024 $ 500.0 $ — $ 500.0

EQUITY EQUITY (Tables)

EQUITY EQUITY (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Quarterly dividends per share paid on common stock	The following table sets forth the quarterly dividends per share paid on our common stock in the periods indicated: Years Ended December 31, 2019 2018 2017 First Quarter $ 0.860 $ 0.770 $ 0.615 Second Quarter 0.865 0.795 0.615 Third Quarter 0.890 0.825 0.745 Fourth Quarter 0.915 0.855 0.745 Total $ 3.53 $ 3.245 $ 2.72

ACCUMULATED OTHER COMPREHENSI_2

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables)	12 Months Ended
	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss)	The following table sets forth the balance in accumulated other comprehensive loss for the periods indicated: Risk- Management Assets/Liabilities (a) Retirement and Other Postretirement Benefit Plan Obligations (a) (b) Risk- Management Assets/Liabilities of Unconsolidated Affiliates (a) Accumulated Other Comprehensive Loss (a) ( Thousands of dollars ) January 1, 2018 $ (81,915 ) $ (105,411 ) $ (1,204 ) $ (188,530 ) Beginning balance adjustments (c) 3,078 (805 ) (2,273 ) — Other comprehensive income (loss) before reclassifications (5,673 ) (8,116 ) 2,396 (11,393 ) Amounts reclassified to net income 36,870 12,887 28 49,785 Other comprehensive income (loss) attributable to ONEOK 31,197 4,771 2,424 38,392 Impact of adoption of ASU 2018-02 (d) (17,020 ) (20,340 ) (741 ) (38,101 ) December 31, 2018 (64,660 ) (121,785 ) (1,794 ) (188,239 ) Other comprehensive loss before reclassifications (147,803 ) (19,490 ) (7,275 ) (174,568 ) Amounts reclassified to net income (21,057 ) 9,794 70 (11,193 ) Other comprehensive income (loss) (168,860 ) (9,696 ) (7,205 ) (185,761 ) December 31, 2019 $ (233,520 ) $ (131,481 ) $ (8,999 ) $ (374,000 ) (a) All amounts are presented net of tax. (b) Includes amounts related to supplemental executive retirement plan. (c) Reclassifications were made between categories to conform to current presentation. (d) We elected to adopt this guidance in the first quarter 2018, which allows a reclassification from accumulated other comprehensive income/loss to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act. After adopting and applying this guidance, our accumulated other comprehensive loss balance does not include stranded taxes resulting from the Tax Cuts and Jobs Act.
Reclassification out of Accumulated Other Comprehensive Income (Loss)	The following table sets forth the effect of reclassifications from accumulated other comprehensive loss to net income for the periods indicated: Details about Accumulated Other Comprehensive Loss Components Years Ended December 31, Affected Line Item in the Consolidated Statements of Income 2019 2018 2017 ( Thousands of dollars ) Risk-management assets/liabilities Commodity contracts $ 50,345 $ (29,596 ) $ (69,561 ) Commodity sales revenues/ cost of sales and fuel Interest-rate contracts (23,230 ) (18,287 ) (21,025 ) Interest expense 27,115 (47,883 ) (90,586 ) Income before income taxes (6,058 ) 11,013 26,899 Income taxes 21,057 (36,870 ) (63,687 ) Net income Noncontrolling interests — — (18,146 ) Less: Net income attributable noncontrolling interests $ 21,057 $ (36,870 ) $ (45,541 ) Net income attributable to ONEOK Retirement and other postretirement benefit plan obligations (a) Amortization of net loss $ (12,946 ) $ (18,398 ) $ (15,265 ) Other income (expense) Amortization of unrecognized prior service credit 227 1,662 1,662 Other income (expense) (12,719 ) (16,736 ) (13,603 ) Income before income taxes 2,925 3,849 5,441 Income taxes $ (9,794 ) $ (12,887 ) $ (8,162 ) Net income attributable to ONEOK Risk-management assets/liabilities of unconsolidated affiliates Interest-rate contracts $ (91 ) $ (36 ) $ (367 ) Equity in net earnings from investments 21 8 97 Income taxes (70 ) (28 ) (270 ) Net income Noncontrolling interests — — (106 ) Less: Net income attributable to noncontrolling interests $ (70 ) $ (28 ) $ (164 ) Net income attributable to ONEOK Total reclassifications for the period attributable to ONEOK $ 11,193 $ (49,785 ) $ (53,867 ) Net income attributable to ONEOK (a) - These components of accumulated other comprehensive loss are included in the computation of net periodic benefit cost. See Note K for additional detail of our net periodic benefit cost.
Schedule of Accumulated Other Comprehensive Income (Loss) for Risk-Management Assets/Liabilities [Table Text Block]	The following table sets forth information about the balance of accumulated other comprehensive loss at December 31, 2019, representing unrealized gains (losses) related to risk-management assets and liabilities: Risk- Management Assets/Liabilities (a) ( Thousands of dollars ) Commodity derivative instruments expected to be realized within the next 24 months (b) $ 28,119 Settled interest-rate swaps to be recognized over the life of the long-term, fixed-rate debt (c) (106,592 ) Interest-rate swaps with future settlement dates expected to be amortized over the life of long-term debt (155,047 ) Accumulated other comprehensive loss at December 31, 2019 $ (233,520 ) (a) - All amounts are presented net of tax. (b) - Based on December 31, 2019, commodity prices, we will realize $28.9 million in net gains, net of tax, over the next 12 months and $0.8 million in net loss, net of tax, thereafter. (c) - Losses of $20.3 million , net of tax, will be reclassified into earnings during the next 12 months as the hedged items affect earnings.

EARNINGS PER SHARE EARNINGS P_2

EARNINGS PER SHARE EARNINGS PER SHARE (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Earnings Per Share	The following tables set forth the computation of basic and diluted EPS for the periods indicated: Year Ended December 31, 2019 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income available for common stock $ 1,277,477 413,560 $ 3.09 Diluted EPS Effect of dilutive securities — 1,884 Net income available for common stock and common stock equivalents $ 1,277,477 415,444 $ 3.07 Year Ended December 31, 2018 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 1,150,603 411,485 $ 2.80 Diluted EPS Effect of dilutive securities — 2,710 Net income attributable to ONEOK available for common stock and common stock equivalents $ 1,150,603 414,195 $ 2.78 Year Ended December 31, 2017 Income Shares Per Share Amount ( Thousands, except per share amounts ) Basic EPS Net income attributable to ONEOK available for common stock $ 387,074 297,477 $ 1.30 Diluted EPS Effect of dilutive securities — 2,303 Net income attributable to ONEOK available for common stock and common stock equivalents $ 387,074 299,780 $ 1.29

SHARE-BASED PAYMENTS SHARE-BA_2

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Restricted Stock Units Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Activity	The following tables set forth activity and various statistics for our restricted stock unit awards: Number of Units Weighted Average Price Nonvested December 31, 2018 1,025,193 $ 34.68 Granted 262,399 $ 58.07 Released to participants (541,871 ) $ 19.73 Forfeited (46,731 ) $ 49.61 Nonvested December 31, 2019 698,990 $ 54.05 2019 2018 2017 Weighted-average grant date fair value (per share) $ 58.07 $ 46.94 $ 45.11 Fair value of units granted (thousands of dollars) $ 15,238 $ 13,907 $ 12,685 Grant date fair value of units vested (thousands of dollars) $ 10,691 $ 9,552 $ 7,258
Performance-Unit Activity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of Share-based Compensation, Activity	The following tables set forth activity and various statistics related to the performance unit awards and the assumptions used in the valuations at the respective grant dates: Number of Units Weighted Average Price Nonvested December 31, 2018 1,243,643 $ 44.08 Granted 338,427 $ 68.02 Released to participants (636,628 ) $ 23.59 Forfeited (7,621 ) $ 39.54 Nonvested December 31, 2019 937,821 $ 66.67 2019 2018 2017 Volatility (a) 27.10% 39.20% 40.59% Dividend yield 5.05% 5.49% 4.68% Risk-free interest rate 2.47% 2.44% 1.49% (a) - Volatility was based on historical volatility over three years using daily stock price observations. 2019 2018 2017 Weighted-average grant date fair value (per share) $ 68.02 $ 59.57 $ 56.65 Fair value of units granted (thousands of dollars) $ 23,020 $ 22,081 $ 17,621 Grant date fair value of units vested (thousands of dollars) $ 15,018 $ 12,545 $ 8,704

EMPLOYEE BENEFIT PLANS EMPLOY_3

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Tables)	12 Months Ended
	Dec. 31, 2019
Defined Benefit Plan [Abstract]
Pension and postretirement benefit plans obligations and fair value of plan assets	Obligations and Funded Status - The following table sets forth our retirement and other postretirement benefit plans benefit obligations and fair value of plan assets for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 Change in benefit obligation ( Thousands of dollars ) Benefit obligation, beginning of period $ 466,994 $ 481,615 $ 46,840 $ 57,938 Service cost 7,825 7,339 468 845 Interest cost 20,528 17,659 2,038 2,108 Plan participants’ contributions — — 1,142 1,050 Actuarial loss (gain) 55,954 (24,345 ) 5,101 (10,233 ) Benefits paid (16,452 ) (15,274 ) (3,280 ) (4,868 ) Benefit obligation, end of period 534,849 466,994 52,309 46,840 Change in plan assets Fair value of plan assets, beginning of period 290,684 306,008 30,800 34,133 Actual return on plan assets 58,060 (12,350 ) 8,087 (998 ) Employer contributions 14,500 12,300 2,000 1,100 Plan participants’ contributions — — 1,142 1,050 Benefits paid (16,452 ) (15,274 ) (2,969 ) (4,485 ) Fair value of plan assets, end of period 346,792 290,684 39,060 30,800 Balance at December 31 $ (188,057 ) $ (176,310 ) $ (13,249 ) $ (16,040 ) Current liabilities $ (4,616 ) $ (4,514 ) $ — $ — Noncurrent liabilities (183,441 ) (171,796 ) (13,249 ) (16,040 ) Balance at December 31 $ (188,057 ) $ (176,310 ) $ (13,249 ) $ (16,040 )
Components of net periodic benefit cost for pension and postretirement benefit plans	Components of Net Periodic Benefit Cost - The following table sets forth the components of net periodic benefit cost for our retirement and other postretirement benefit plans for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2019 2018 2017 2019 2018 2017 ( Thousands of dollars ) Components of net periodic benefit cost Service cost $ 7,825 $ 7,339 $ 6,896 $ 468 $ 845 $ 662 Interest cost 20,528 17,659 18,645 2,038 2,108 2,261 Expected return on plan assets (23,600 ) (23,917 ) (21,376 ) (2,285 ) (2,690 ) (2,257 ) Amortization of prior service credit — — — (227 ) (1,662 ) (1,662 ) Amortization of net loss 12,649 17,060 13,586 297 1,338 1,679 Net periodic benefit cost $ 17,402 $ 18,141 $ 17,751 $ 291 $ (61 ) $ 683
Amounts recognized in other comprehensive income (loss)	Other Comprehensive Income (Loss) - The following table sets forth the amounts recognized in other comprehensive income (loss) related to our retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits Years Ended December 31, Years Ended December 31, 2019 2018 2017 2019 2018 2017 ( Thousands of dollars ) Net gain (loss) $ (25,389 ) $ (16,351 ) $ (16,572 ) $ 700 $ 6,545 $ (328 ) Prior service cost (601 ) — — — — — Amortization of prior service credit — — — (227 ) (1,662 ) (1,662 ) Amortization of net loss 12,649 17,060 13,586 297 1,338 1,679 Deferred income taxes (a) 3,068 (18,928 ) (960 ) (177 ) (2,831 ) 82 Total recognized in other comprehensive income (loss) $ (10,273 ) $ (18,219 ) $ (3,946 ) $ 593 $ 3,390 $ (229 ) (a) - Year ended December 31, 2018, includes the impact of adopting ASU 2018-02, “Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income.”
Amounts in accumulated other comprehensive income (loss)	The table below sets forth the amounts in accumulated other comprehensive loss that had not yet been recognized as components of net periodic benefit expense for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 ( Thousands of dollars ) Prior service credit (cost) $ (601 ) $ — $ — $ 227 Accumulated loss (172,952 ) (160,212 ) (4,110 ) (5,108 ) Accumulated other comprehensive loss (173,553 ) (160,212 ) (4,110 ) (4,881 ) Deferred income taxes 46,354 43,286 1,389 1,567 Accumulated other comprehensive loss, net of tax $ (127,199 ) $ (116,926 ) $ (2,721 ) $ (3,314 )
Weighted-average assumptions used to determine benefit obligations and net periodic benefit costs	Actuarial Assumptions - The following table sets forth the weighted-average assumptions used to determine benefit obligations for retirement and other postretirement benefits for the periods indicated: Retirement Benefits Other Postretirement Benefits December 31, December 31, 2019 2018 2019 2018 Discount rate 3.50% 4.50% 3.50% 4.50% Compensation increase rate 3.70% 3.65% NA NA The following table sets forth the weighted-average assumptions used to determine net periodic benefit costs for the periods indicated: Years Ended December 31, 2019 2018 2017 Discount rate - retirement plans 4.50% 3.75% 4.50% Discount rate - other postretirement plans 4.50% 3.75% 4.25% Expected long-term return on plan assets 7.50% 8.00% 7.75% Compensation increase rate 3.65% 3.00% 3.10%
Assumed health care cost trend rates	Health Care Cost Trend Rates - The following table sets forth the assumed health care cost-trend rates for the periods indicated: 2019 2018 Health care cost-trend rate assumed for next year 7.00% 6.50% Rate to which the cost-trend rate is assumed to decline (the ultimate trend rate) 5.00% 5.00% Year that the rate reaches the ultimate trend rate 2024 2022
Schedule of allocation of plan assets	Plan Assets - Our investment strategy is to invest plan assets in accordance with sound investment practices that emphasize long-term fundamentals. The goal of this strategy is to maximize investment returns while managing risk in order to meet the plan’s current and projected financial obligations. The investment policy for our defined benefit pension plan follows a glide path approach toward liability-driven investing that shifts a higher portfolio weighting to fixed income as the plan’s funded status increases. The purpose of liability-driven investing is to structure the asset portfolio to more closely resemble the pension liability and thereby more effectively hedge against changes in the liability. The plan’s current investments include a diverse blend of various domestic and international equities, investments in various classes of debt securities, real estate and hedge funds. The target allocation for the assets of our retirement plan as of December 31, 2019, is as follows: Domestic and international equities 42 % Long duration fixed income 30 % Return-seeking credit 11 % Hedge funds 10 % Real estate funds 7 % Total 100 % As part of our risk management for the plans, minimums and maximums have been set for each of the asset classes listed above. The following tables set forth the plan assets by fair value category as of the measurement date for our defined benefit pension and other postretirement benefit plans: Pension Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 47 $ — $ — $ 47 $ 149,985 $ 150,032 Real estate funds — — — — 23,885 23,885 Government obligations — — — — 50,708 50,708 Corporate obligations (b) — — — — 85,898 85,898 Common/collective trusts — 3,263 — 3,263 — 3,263 Cash 63 — — 63 — 63 Other investments (c) — — — — 32,943 32,943 Fair value of plan assets $ 110 $ 3,263 $ — $ 3,373 $ 343,419 $ 346,792 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category repre sen ts alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no u nfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Pension Benefits December 31, 2018 Asset Category Level 1 Level 2 Level 3 Subtotal Measured at NAV (d) Total ( Thousands of dollars ) Investments: Equity securities (a) $ 58 $ — $ — $ 58 $ 116,790 $ 116,848 Real estate funds — — — — 20,569 20,569 Government obligations — — — — 48,913 48,913 Corporate obligations (b) — — — — 69,377 69,377 Common/collective trusts — 3,961 — 3,961 — 3,961 Cash 95 — — 95 — 95 Other investments (c) — — — — 30,921 30,921 Fair value of plan assets $ 153 $ 3,961 $ — $ 4,114 $ 286,570 $ 290,684 (a) - This category represents securities of the respective market sector from diverse industries. (b) - This category represents bonds from diverse industries. (c) - This category represents alternative investments in limited partnerships, which can be redeemed with a 30-day notice with no further restrictions. There are no unfunded capital commitments. (d) - Plan asset investments measured at fair value using the net asset value per share. Other Postretirement Benefits December 31, 2019 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) $ 2,043 $ — $ — $ 2,043 Money market funds — 2,428 — 2,428 Insurance and group annuity contracts — 34,589 — 34,589 Fair value of plan assets $ 2,043 $ 37,017 $ — $ 39,060 (a) - This category represents securities of the respective market sector from diverse industries. Other Postretirement Benefits December 31, 2018 Asset Category Level 1 Level 2 Level 3 Total ( Thousands of dollars ) Investments: Equity securities (a) $ 1,792 $ — $ — $ 1,792 Money market funds 1 413 — 414 Insurance and group annuity contracts — 28,594 — 28,594 Fair value of plan assets $ 1,793 $ 29,007 $ — $ 30,800 (a) - This category represents securities of the respective market sector from diverse industries.
Pension benefits and postretirement benefit payments expected to be paid	The following table sets forth the defined benefit pension and other postretirement benefits payments expected to be paid in 2020 through 2029: Pension Benefits Other Postretirement Benefits Benefits to be paid in: ( Thousands of dollars ) 2020 $ 18,277 $ 3,422 2021 $ 19,252 $ 3,399 2022 $ 20,202 $ 3,519 2023 $ 21,170 $ 3,454 2024 $ 22,228 $ 3,446 2025 through 2029 $ 123,959 $ 16,385

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Provision for Income Taxes	The following table sets forth our provision for income taxes for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Current tax expense (benefit) Federal $ (1,278 ) $ 260 $ 295 State 963 1,633 1,670 Total current tax expense (benefit) (315 ) 1,893 1,965 Deferred tax expense Federal 327,806 319,551 376,728 State 44,923 41,459 68,589 Total deferred tax expense 372,729 361,010 445,317 Total provision for income taxes $ 372,414 $ 362,903 $ 447,282
Reconciliation of Income Tax Provision	The following table is a reconciliation of our income tax provision for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Income before income taxes $ 1,650,991 $ 1,517,935 $ 1,040,801 Less: Net income attributable to noncontrolling interests — 3,329 205,678 Net income attributable to ONEOK before income taxes 1,650,991 1,514,606 835,123 Federal statutory income tax rate 21.0 % 21.0 % 35.0 % Provision for federal income taxes 346,708 318,067 292,293 State income taxes, net of federal benefit 34,545 38,668 16,197 Deferred tax rate change, inclusive of valuation allowance 11,340 5,552 141,283 Excess tax benefits from share-based compensation (20,983 ) (4,644 ) — Other, net 804 5,260 (2,491 ) Income tax provision $ 372,414 $ 362,903 $ 447,282
Schedule of Deferred Tax Assets and Liabilities	The following table sets forth the tax effects of temporary differences that gave rise to significant portions of the deferred tax assets and liabilities for the periods indicated: December 31, December 31, Deferred tax assets ( Thousands of dollars ) Employee benefits and other accrued liabilities $ 99,510 $ 91,587 Federal net operating loss 858,030 420,318 State net operating loss and benefits 171,779 108,004 Derivative instruments 83,710 22,108 Other 12,769 13,378 Total deferred tax assets 1,225,798 655,395 Valuation allowance for state net operating loss and tax credits Carryforward expected to expire prior to utilization (94,794 ) (73,820 ) Net deferred tax assets 1,131,004 581,575 Deferred tax liabilities Excess of tax over book depreciation 84,631 73,113 Investment in partnerships (a) 1,582,436 728,193 Total deferred tax liabilities 1,667,067 801,306 Net deferred tax assets (liabilities) $ (536,063 ) $ (219,731 ) (a) Due primarily to excess of tax over book depreciation.

UNCONSOLIDATED AFFILIATES (Tabl

UNCONSOLIDATED AFFILIATES (Tables)	12 Months Ended
	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments	Investments in Unconsolidated Affiliates - The following table sets forth our investments in unconsolidated affiliates for the periods indicated: Net Ownership Interest December 31, December 31, ( Thousands of dollars ) Northern Border Pipeline 50% $ 307,209 $ 381,623 Overland Pass Pipeline 50% 417,473 429,295 Roadrunner 50% 80,816 93,857 Other Various 56,346 64,375 Investments in unconsolidated affiliates (a) $ 861,844 $ 969,150 (a) - Equity-method goodwill (Note A ) was $38.8 million at December 31, 2019 and 2018 .
Equity In Net Earnings From Investments
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments	Equity in Net Earnings from Investments and Impairments - The following table sets forth our equity in net earnings from investments for the periods indicated: Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Northern Border Pipeline $ 68,871 $ 67,854 $ 68,153 Overland Pass Pipeline 63,698 65,887 60,067 Roadrunner 26,839 22,993 19,150 Other (4,867 ) 1,649 11,908 Equity in net earnings from investments $ 154,541 $ 158,383 $ 159,278 Impairment of equity investments $ — $ — $ (4,270 )
Unconsolidated Affiliates Financial Information
Schedule of Equity Method Investments [Line Items]
Schedule of Equity Method Investments	Unconsolidated Affiliates Financial Information - The following tables set forth summarized combined financial information of our unconsolidated affiliates for the periods indicated: December 31, December 31, ( Thousands of dollars ) Balance Sheet Current assets $ 149,564 $ 158,723 Property, plant and equipment, net $ 2,314,631 $ 2,413,662 Other noncurrent assets $ 13,252 $ 16,273 Current liabilities $ 88,142 $ 83,057 Long-term debt $ 581,327 $ 480,731 Other noncurrent liabilities $ 76,685 $ 47,826 Accumulated other comprehensive income (loss) $ (28,373 ) $ 2,053 Owners’ equity $ 1,759,666 $ 1,974,991 Years Ended December 31, 2019 2018 2017 ( Thousands of dollars ) Income Statement Revenues $ 634,135 $ 637,762 $ 639,102 Operating expenses $ 291,210 $ 276,373 $ 277,121 Net income $ 315,274 $ 337,694 $ 347,692 Distributions paid to us (a) $ 257,644 $ 197,285 $ 196,114 (a) As determined by the Northern Border Pipeline Management Committee, we received an additional distribution of $50.0 million from Northern Border Pipeline during the year ended December 31, 2019.

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Rental Payments for Firm Transportation, Storage Contracts and Capital Leases	The following table sets forth our firm transportation and storage contract payments for the periods indicated: Firm Transportation and Storage Contracts ( Millions of dollars ) 2020 $ 61.6 2021 48.1 2022 40.1 2023 36.4 2024 34.3 Thereafter 177.9 Total $ 398.4

LEASES (Tables)

LEASES (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The following table sets forth the maturity of our lease liabilities as of December 31, 2019: Finance Lease Operating Leases ( Millions of dollars ) 2020 $ 4.5 $ 2.5 2021 4.5 2.1 2022 4.5 2.0 2023 4.5 1.9 2024 4.5 1.9 2025 and beyond 17.1 9.2 Total lease payments 39.6 19.6 Less: Interest 13.4 4.2 Present value of lease liabilities $ 26.2 $ 15.4
LeaseAssetsAndLiabilitiesInBalanceSheet [Table Text Block]	The following table sets forth information about our lease assets and liabilities included in our Consolidated Balance Sheet for the period indicated: Leases Location in our Consolidated Balance Sheet December 31, 2019 ( Thousands of dollars ) Assets Operating leases Other assets $ 15,147 Finance lease Property, plant and equipment 28,286 Finance lease Accumulated depreciation (1,320 ) Total leased assets $ 42,113 Liabilities Current Operating leases Other current liabilities $ 1,883 Finance lease Finance lease liability 1,949 Noncurrent Operating leases Other deferred credits 13,509 Finance lease Finance lease liability 24,296 Total lease liabilities $ 41,637 The following table sets forth supplemental information about our cash flows: Year Ended December 31, 2019 ( Thousands of dollars ) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows for operating leases $ 6,213 Financing cash flows for finance lease $ 1,764 Right-of-use assets obtained in exchange for operating lease liabilities (noncash) $ 4,097
Lease, Cost [Table Text Block]	The following table sets forth information about our leases for the period indicated: Year Ended December 31, 2019 At December 31, 2019 Location in our Consolidated Statement of Income Lease Cost Weighted-Average Remaining Lease Term Weighted-Average Discount Rate (a) ( Thousands of dollars ) ( Years ) Operating leases Operations and maintenance $ 6,803 10.4 4.58% Finance lease 8.8 10.00% Amortization of lease assets Depreciation and amortization 1,131 Interest on lease liabilities Interest expense 2,721 Total lease cost $ 10,655 (a) - Our weighted-average discount rates represent the rate implicit in the lease or our incremental borrowing rate for a term equal to the remaining term of the lease.
Finance Lease, Liability, Maturity [Table Text Block]	The following table sets forth the maturity of our lease liabilities as of December 31, 2019: Finance Lease Operating Leases ( Millions of dollars ) 2020 $ 4.5 $ 2.5 2021 4.5 2.1 2022 4.5 2.0 2023 4.5 1.9 2024 4.5 1.9 2025 and beyond 17.1 9.2 Total lease payments 39.6 19.6 Less: Interest 13.4 4.2 Present value of lease liabilities $ 26.2 $ 15.4

REVENUES (Tables)

REVENUES (Tables)	12 Months Ended
	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset and Liability [Table Text Block]	The following tables set forth the changes in our contract asset and contract liability balances for the periods indicated: Contract Assets ( Millions of dollars ) Balance at January 1, 2018 (a) $ 6.4 Amounts invoiced in excess of revenue recognized (0.9 ) Net additions 0.7 Balance at December 31, 2018 (b) 6.2 Amounts invoiced in excess of revenue recognized (1.7 ) Net additions 0.5 Balance at December 31, 2019 (c) $ 5.0 (a) - Balance includes $0.9 million of current assets. (b) - Contract assets of $1.7 million and $4.5 million are included in other current assets and other assets, respectively, in our Consolidated Balance Sheet. (c) - Contract assets of $1.3 million and $3.7 million are included in other current assets and other assets, respectively, in our Consolidated Balance Sheet. Contract Liabilities ( Millions of dollars ) Balance at January 1, 2018 (a) $ 33.3 Revenue recognized included in beginning balance (19.5 ) Net additions 17.9 Balance at December 31, 2018 (b) 31.7 Revenue recognized included in beginning balance (15.6 ) Net additions 41.0 Balance at December 31, 2019 (c) $ 57.1 (a) - Balance includes $19.5 million of current liabilities. (b) - Contract liabilities of $15.6 million and $16.1 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet. (c) - Contract liabilities of $22.2 million and $34.9 million are included in other current liabilities and other deferred credits, respectively, in our Consolidated Balance Sheet.
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table presents aggregate value allocated to unsatisfied performance obligations as of December 31, 2019, and the amounts we expect to recognize in revenue in future periods, related primarily to firm transportation and storage contracts with remaining contract terms ranging from one month to 24 years : Expected Period of Recognition in Revenue ( Millions of dollars ) 2020 $ 343.5 2021 290.4 2022 214.8 2023 166.4 2024 and beyond 807.2 Total estimated transaction price allocated to unsatisfied performance obligations $ 1,822.3

SEGMENTS (Tables)

SEGMENTS (Tables)	12 Months Ended
	Dec. 31, 2019
Segment Reporting, Disclosure of Entity's Reportable Segments [Abstract]
Segments	Operating Segment Information - The following tables set forth certain selected financial information for our operating segments for the periods indicated: Year Ended December 31, 2019 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) NGL and condensate sales $ 1,224,378 $ 7,910,833 $ — $ 9,135,211 Residue natural gas sales 966,149 — 1,244 967,393 Gathering, processing and exchange services revenue 164,299 414,238 — 578,537 Transportation and storage revenue — 197,483 466,266 663,749 Other 13,813 9,962 4,477 28,252 Total revenues (c) 2,368,639 8,532,516 471,987 11,373,142 Cost of sales and fuel (exclusive of depreciation and operating costs) (1,302,310 ) (6,690,918 ) (4,628 ) (7,997,856 ) Operating costs (368,352 ) (456,892 ) (157,230 ) (982,474 ) Equity in net earnings from investments (6,292 ) 65,123 95,710 154,541 Noncash compensation expense and other 10,965 15,936 2,977 29,878 Segment adjusted EBITDA $ 702,650 $ 1,465,765 $ 408,816 $ 2,577,231 Depreciation and amortization $ (219,519 ) $ (196,132 ) $ (57,250 ) $ (472,901 ) Investments in unconsolidated affiliates $ 34,426 $ 439,393 $ 388,025 $ 861,844 Total assets $ 6,795,744 $ 12,551,476 $ 2,094,072 $ 21,441,292 Capital expenditures $ 926,489 $ 2,796,604 $ 99,221 $ 3,822,314 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.4 billion , of which $1.2 billion related to sales within the segment, and cost of sales and fuel of $496.8 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $285.3 million and cost of sales and fuel of $20.0 million . (c) - Intersegment revenues for the Natural Gas Gathering and Processing segment totaled $1.2 billion . Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2019 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 9,135,211 $ (1,190,424 ) $ 7,944,787 Residue natural gas sales 967,393 (1,418 ) 965,975 Gathering, processing and exchange services revenue 578,537 — 578,537 Transportation and storage revenue 663,749 (15,646 ) 648,103 Other 28,252 (1,287 ) 26,965 Total revenues (a) $ 11,373,142 $ (1,208,775 ) $ 10,164,367 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (7,997,856 ) $ 1,209,816 $ (6,788,040 ) Operating costs $ (982,474 ) $ (390 ) $ (982,864 ) Depreciation and amortization $ (472,901 ) $ (3,634 ) $ (476,535 ) Equity in net earnings from investments $ 154,541 $ — $ 154,541 Investments in unconsolidated affiliates $ 861,844 $ — $ 861,844 Total assets $ 21,441,292 $ 370,829 $ 21,812,121 Capital expenditures $ 3,822,314 $ 26,035 $ 3,848,349 (a) - Noncustomer revenue for the year ended December 31, 2019, totaled $139.6 million related primarily to gains from derivatives on commodity contracts. Year Ended December 31, 2018 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) NGL and condensate sales $ 1,775,991 $ 10,319,847 $ — $ 12,095,838 Residue natural gas sales 1,084,162 — 9,772 1,093,934 Gathering, processing and exchange services revenue 163,194 404,897 — 568,091 Transportation and storage revenue — 199,018 414,969 613,987 Other 11,230 10,816 6,994 29,040 Total revenues (c) 3,034,577 10,934,578 431,735 14,400,890 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,041,448 ) (9,176,813 ) (15,984 ) (11,234,245 ) Operating costs (368,939 ) (394,115 ) (144,259 ) (907,313 ) Equity in net earnings from investments 410 67,126 90,847 158,383 Noncash compensation expense and other 7,007 9,829 3,912 20,748 Segment adjusted EBITDA $ 631,607 $ 1,440,605 $ 366,251 $ 2,438,463 Depreciation and amortization $ (196,090 ) $ (174,007 ) $ (55,118 ) $ (425,215 ) Investments in unconsolidated affiliates $ 42,630 $ 451,040 $ 475,480 $ 969,150 Total assets $ 6,078,473 $ 9,663,640 $ 2,131,669 $ 17,873,782 Capital expenditures $ 694,611 $ 1,306,341 $ 119,185 $ 2,120,137 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion , of which $1.1 billion related to sales within the segment, and cost of sales and fuel of $506.0 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $266.6 million and cost of sales and fuel of $26.0 million . (c) - Intersegment revenues for the Natural Gas Gathering and Processing segment totaled $1.8 billion . Intersegment revenues for the Natural Gas Liquids and Natural Gas Pipelines segments were not material. Year Ended December 31, 2018 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated NGL and condensate sales $ 12,095,838 $ (1,794,342 ) $ 10,301,496 Residue natural gas sales 1,093,934 (2,832 ) 1,091,102 Gathering, processing and exchange services revenue 568,091 (21 ) 568,070 Transportation and storage revenue 613,987 (10,550 ) 603,437 Other 29,040 51 29,091 Total revenues (a) $ 14,400,890 $ (1,807,694 ) $ 12,593,196 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,234,245 ) $ 1,811,537 $ (9,422,708 ) Operating costs $ (907,313 ) $ 245 $ (907,068 ) Depreciation and amortization $ (425,215 ) $ (3,342 ) $ (428,557 ) Equity in net earnings from investments $ 158,383 $ — $ 158,383 Investments in unconsolidated affiliates $ 969,150 $ — $ 969,150 Total assets $ 17,873,782 $ 357,889 $ 18,231,671 Capital expenditures $ 2,120,137 $ 21,338 $ 2,141,475 (a) - Noncustomer revenue for the year ended December 31, 2018, totaled $(16.2) million related primarily to losses from derivatives on commodity contracts. Year Ended December 31, 2017 Natural Gas Gathering and Processing Natural Gas Liquids (a) Natural Gas Pipelines (b) Total Segments ( Thousands of dollars ) Sales to unaffiliated customers $ 1,750,655 $ 10,009,576 $ 411,490 $ 12,171,721 Intersegment revenues 1,275,919 616,628 8,442 1,900,989 Total revenues 3,026,574 10,626,204 419,932 14,072,710 Cost of sales and fuel (exclusive of depreciation and operating costs) (2,216,355 ) (9,176,494 ) (43,424 ) (11,436,273 ) Operating costs (307,376 ) (358,278 ) (125,308 ) (790,962 ) Equity in net earnings from investments 12,098 59,876 87,304 159,278 Other 3,531 3,631 1,314 8,476 Segment adjusted EBITDA $ 518,472 $ 1,154,939 $ 339,818 $ 2,013,229 Depreciation and amortization $ (184,923 ) $ (167,277 ) $ (51,025 ) $ (403,225 ) Impairment of long-lived assets and equity investments $ (20,240 ) $ — $ — $ (20,240 ) Investments in unconsolidated affiliates $ 55,841 $ 457,467 $ 489,848 $ 1,003,156 Total assets $ 5,495,163 $ 8,782,700 $ 2,055,020 $ 16,332,883 Capital expenditures $ 284,205 $ 114,267 $ 95,564 $ 494,036 (a) - Our Natural Gas Liquids segment has regulated and nonregulated operations. Our Natural Gas Liquids segment’s regulated operations had revenues of $1.2 billion , of which $1.0 billion related to sales within the segment, and cost of sales and fuel of $497.4 million . (b) - Our Natural Gas Pipelines segment has regulated and nonregulated operations. Our Natural Gas Pipelines segment’s regulated operations had revenues of $264.9 million and cost of sales and fuel of $44.0 million . Year Ended December 31, 2017 Total Segments Other and Eliminations Total ( Thousands of dollars ) Reconciliations of total segments to consolidated Sales to unaffiliated customers $ 12,171,721 $ 2,186 $ 12,173,907 Intersegment revenues 1,900,989 (1,900,989 ) — Total revenues $ 14,072,710 $ (1,898,803 ) $ 12,173,907 Cost of sales and fuel (exclusive of depreciation and operating costs) $ (11,436,273 ) $ 1,898,228 $ (9,538,045 ) Operating costs $ (790,962 ) $ (31,748 ) $ (822,710 ) Depreciation and amortization $ (403,225 ) $ (3,110 ) $ (406,335 ) Impairment of long-lived assets and equity investments $ (20,240 ) $ — $ (20,240 ) Equity in net earnings from investments $ 159,278 $ — $ 159,278 Investments in unconsolidated affiliates $ 1,003,156 $ — $ 1,003,156 Total assets $ 16,332,883 $ 513,054 $ 16,845,937 Capital expenditures $ 494,036 $ 18,357 $ 512,393 Years Ended December 31, 2019 2018 2017 Reconciliation of net income to total segment adjusted EBITDA ( Thousands of dollars ) Net income $ 1,278,577 $ 1,155,032 $ 593,519 Add: Interest expense, net of capitalized interest 491,773 469,620 485,658 Depreciation and amortization 476,535 428,557 406,335 Income taxes 372,414 362,903 447,282 Impairment charges — — 20,240 Noncash compensation expense 26,699 37,954 13,421 Other corporate costs and noncash items (a) (68,767 ) (15,603 ) 46,774 Total segment adjusted EBITDA $ 2,577,231 $ 2,438,463 $ 2,013,229 (a) - The year ended December 31, 2019, includes higher equity AFUDC related to our capital-growth projects compared with 2018 and 2017. The year ended December 31, 2017, includes our April 2017 $20.0 million contribution of Series E Preferred Stock to the Foundation and costs related to the Merger Transaction of $30.0 million .

QUARTERLY FINANCIAL DATA (UNA_2

QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Data [Abstract]
Quarterly Financial Data	Year Ended December 31, 2019 First Quarter Second Quarter Third Quarter Fourth Quarter ( Thousands of dollars, except per share amounts ) Total revenues $ 2,779,958 $ 2,457,575 $ 2,263,228 $ 2,663,606 Operating income $ 468,742 $ 476,146 $ 482,151 $ 487,314 Net income $ 337,208 $ 311,963 $ 309,155 $ 320,251 Net income available to common shareholders $ 336,933 $ 311,688 $ 308,880 $ 319,976 Earnings per share total Basic $ 0.82 $ 0.75 $ 0.75 $ 0.77 Diluted $ 0.81 $ 0.75 $ 0.74 $ 0.77 Year Ended December 31, 2018 First Quarter Second Quarter Third Quarter Fourth Quarter ( Thousands of dollars except per share amounts ) Total revenues $ 3,102,077 $ 2,960,529 $ 3,393,890 $ 3,136,700 Operating income $ 419,699 $ 448,366 $ 495,534 $ 471,865 Net income $ 266,049 $ 282,179 $ 313,916 $ 292,888 Net income available to common shareholders $ 264,233 $ 280,773 $ 312,984 $ 292,613 Earnings per share total Basic $ 0.65 $ 0.68 $ 0.76 $ 0.71 Diluted $ 0.64 $ 0.68 $ 0.75 $ 0.70

SUPPLEMENTAL CONDENSED CONSOL_2

SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2019
Condensed Financial Information Disclosure [Abstract]
Condensed Consolidating Statements of Income	Year Ended December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 8,916.1 $ — $ 8,916.1 Services — — — 1,250.4 (2.1 ) 1,248.3 Total revenues — — — 10,166.5 (2.1 ) 10,164.4 Cost of sales and fuel (exclusive of items shown separately below) — — — 6,788.0 — 6,788.0 Operating expenses — — — 1,461.5 (2.1 ) 1,459.4 (Gain) loss on sale of assets — — 2.7 (0.1 ) — 2.6 Operating income — — (2.7 ) 1,917.1 — 1,914.4 Equity in net earnings from investments 1,898.7 1,906.2 1,908.9 116.3 (5,675.6 ) 154.5 Other income (expense), net 34.4 305.7 308.3 42.1 (616.6 ) 73.9 Interest expense, net (287.4 ) (308.3 ) (308.3 ) (204.4 ) 616.6 (491.8 ) Income before income taxes 1,645.7 1,903.6 1,906.2 1,871.1 (5,675.6 ) 1,651.0 Income taxes (367.1 ) — — (5.3 ) — (372.4 ) Net income 1,278.6 1,903.6 1,906.2 1,865.8 (5,675.6 ) 1,278.6 Less: Preferred stock dividends 1.1 — — — — 1.1 Net income available to common shareholders $ 1,277.5 $ 1,903.6 $ 1,906.2 $ 1,865.8 $ (5,675.6 ) $ 1,277.5 Net income $ 1,278.6 $ 1,903.6 $ 1,906.2 $ 1,865.8 $ (5,675.6 ) $ 1,278.6 Other comprehensive income (loss), net of tax (183.8 ) (2.6 ) (20.9 ) (20.5 ) 42.0 (185.8 ) Comprehensive income $ 1,094.8 $ 1,901.0 $ 1,885.3 $ 1,845.3 $ (5,633.6 ) $ 1,092.8 Year Ended December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 11,395.6 $ — $ 11,395.6 Services — — — 1,199.7 (2.1 ) 1,197.6 Total revenues — — — 12,595.3 (2.1 ) 12,593.2 Cost of sales and fuel (exclusive of items shown separately below) — — — 9,422.7 — 9,422.7 Operating expenses (0.6 ) — — 1,338.3 (2.1 ) 1,335.6 Gain on sale of assets — — — (0.6 ) — (0.6 ) Operating income 0.6 — — 1,834.9 — 1,835.5 Equity in net earnings from investments 1,655.6 1,660.5 1,660.5 116.3 (4,934.5 ) 158.4 Other income (expense), net 29.6 315.1 315.1 (36.0 ) (630.2 ) (6.4 ) Interest expense, net (179.4 ) (315.1 ) (315.1 ) (290.2 ) 630.2 (469.6 ) Income before income taxes 1,506.4 1,660.5 1,660.5 1,625.0 (4,934.5 ) 1,517.9 Income taxes (354.7 ) — — (8.2 ) — (362.9 ) Net income 1,151.7 1,660.5 1,660.5 1,616.8 (4,934.5 ) 1,155.0 Less: Net income attributable to noncontrolling interests — — — 3.3 — 3.3 Net income attributable to ONEOK 1,151.7 1,660.5 1,660.5 1,613.5 (4,934.5 ) 1,151.7 Less: Preferred stock dividends 1.1 — — — — 1.1 Net income available to common shareholders $ 1,150.6 $ 1,660.5 $ 1,660.5 $ 1,613.5 $ (4,934.5 ) $ 1,150.6 Net income $ 1,151.7 $ 1,660.5 $ 1,660.5 $ 1,616.8 $ (4,934.5 ) $ 1,155.0 Other comprehensive income (loss), net of tax (39.5 ) 101.1 85.9 62.6 (171.7 ) 38.4 Comprehensive income 1,112.2 1,761.6 1,746.4 1,679.4 (5,106.2 ) 1,193.4 Less: Comprehensive income attributable to noncontrolling interests — — — 3.3 — 3.3 Comprehensive income attributable to ONEOK $ 1,112.2 $ 1,761.6 $ 1,746.4 $ 1,676.1 $ (5,106.2 ) $ 1,190.1 Year Ended December 31, 2017 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Revenues Commodity sales $ — $ — $ — $ 9,862.7 $ — $ 9,862.7 Services — — — 2,313.2 (2.0 ) 2,311.2 Total revenues — — — 12,175.9 (2.0 ) 12,173.9 Cost of sales and fuel (exclusive of items shown separately below) — — — 9,538.0 — 9,538.0 Operating expenses 17.8 — 9.2 1,204.0 (2.0 ) 1,229.0 Impairment of long-lived assets — — — 16.0 — 16.0 Gain on sale of assets — — — (0.9 ) — (0.9 ) Operating income (17.8 ) — (9.2 ) 1,418.8 — 1,391.8 Equity in net earnings from investments 1,236.6 1,215.7 1,224.9 100.7 (3,618.6 ) 159.3 Impairment of equity investments — — — (4.3 ) — (4.3 ) Other income (expense), net (12.3 ) 353.1 353.1 (8.0 ) (706.2 ) (20.3 ) Interest expense, net (137.1 ) (353.1 ) (353.1 ) (348.6 ) 706.2 (485.7 ) Income before income taxes 1,069.4 1,215.7 1,215.7 1,158.6 (3,618.6 ) 1,040.8 Income taxes (480.2 ) — — 32.9 — (447.3 ) Net income 589.2 1,215.7 1,215.7 1,191.5 (3,618.6 ) 593.5 Less: Net income attributable to noncontrolling interests 201.4 — — 4.3 — 205.7 Net income attributable to ONEOK 387.8 1,215.7 1,215.7 1,187.2 (3,618.6 ) 387.8 Less: Preferred stock dividends 0.8 — — — — 0.8 Net income available to common shareholders $ 387.0 $ 1,215.7 $ 1,215.7 $ 1,187.2 $ (3,618.6 ) $ 387.0 Net income $ 589.2 $ 1,215.7 $ 1,215.7 $ 1,191.5 $ (3,618.6 ) $ 593.5 Other comprehensive income (loss), net of tax 17.4 13.2 27.9 34.5 (55.9 ) 37.1 Comprehensive income 606.6 1,228.9 1,243.6 1,226.0 (3,674.5 ) 630.6 Less: Comprehensive income attributable to noncontrolling interests 232.4 — — 4.3 — 236.7 Comprehensive income attributable to ONEOK $ 374.2 $ 1,228.9 $ 1,243.6 $ 1,221.7 $ (3,674.5 ) $ 393.9
Condensed Consolidating Balance Sheets	December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total Assets ( Millions of dollars ) Current assets Cash and cash equivalents $ 21.0 $ — $ — $ — $ — $ 21.0 Accounts receivable, net — — — 835.1 — 835.1 Materials and supplies — — — 201.7 — 201.7 Natural gas and NGLs in storage — — — 304.9 — 304.9 Other current assets 12.4 — — 95.2 — 107.6 Total current assets 33.4 — — 1,436.9 — 1,470.3 Property, plant and equipment Property, plant and equipment 166.6 — — 21,884.9 — 22,051.5 Accumulated depreciation and amortization 99.5 — — 3,603.3 — 3,702.8 Net property, plant and equipment 67.1 — — 18,281.6 — 18,348.7 Investments and other assets Investments 6,732.6 4,101.4 11,466.3 769.9 (22,208.4 ) 861.8 Intercompany notes receivable 8,950.9 6,903.2 — — (15,854.1 ) — Other assets 139.9 — — 992.1 (0.7 ) 1,131.3 Total investments and other assets 15,823.4 11,004.6 11,466.3 1,762.0 (38,063.2 ) 1,993.1 Total assets $ 15,923.9 $ 11,004.6 $ 11,466.3 $ 21,480.5 $ (38,063.2 ) $ 21,812.1 Liabilities and equity Current liabilities Current maturities of long-term debt $ — $ — $ — $ 7.7 $ — $ 7.7 Short-term borrowings 220.0 — — — — 220.0 Accounts payable 23.8 — — 1,186.1 — 1,209.9 Other current liabilities 243.8 63.3 — 275.6 — 582.7 Total current liabilities 487.6 63.3 — 1,469.4 — 2,020.3 Intercompany payables — — 7,364.9 8,489.2 (15,854.1 ) — Long-term debt, excluding current maturities 8,421.1 4,045.1 — 13.5 — 12,479.7 Deferred credits and other liabilities Deferred income taxes 417.1 — — 119.7 (0.7 ) 536.1 Other deferred credits 372.1 — — 177.9 — 550.0 Total deferred credits and other liabilities 789.2 — — 297.6 (0.7 ) 1,086.1 Commitments and contingencies Equity 6,226.0 6,896.2 4,101.4 11,210.8 (22,208.4 ) 6,226.0 Total liabilities and equity $ 15,923.9 $ 11,004.6 $ 11,466.3 $ 21,480.5 $ (38,063.2 ) $ 21,812.1 December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total Assets ( Millions of dollars ) Current assets Cash and cash equivalents $ 12.0 $ — $ — $ — $ — $ 12.0 Accounts receivable, net — — — 819.0 — 819.0 Materials and supplies — — — 141.2 — 141.2 Natural gas and NGLs in storage — — — 296.7 — 296.7 Other current assets 29.1 — — 100.6 — 129.7 Total current assets 41.1 — — 1,357.5 — 1,398.6 Property, plant and equipment Property, plant and equipment 145.5 — — 17,885.5 — 18,031.0 Accumulated depreciation and amortization 92.0 — — 3,172.3 — 3,264.3 Net property, plant and equipment 53.5 — — 14,713.2 — 14,766.7 Investments and other assets Investments 6,153.5 3,548.1 9,721.6 791.1 (19,245.1 ) 969.2 Intercompany notes receivable 5,308.6 7,701.5 1,528.0 — (14,538.1 ) — Other assets 115.9 — — 982.3 (1.0 ) 1,097.2 Total investments and other assets 11,578.0 11,249.6 11,249.6 1,773.4 (33,784.2 ) 2,066.4 Total assets $ 11,672.6 $ 11,249.6 $ 11,249.6 $ 17,844.1 $ (33,784.2 ) $ 18,231.7 Liabilities and equity Current liabilities Current maturities of long-term debt $ — $ 500.0 $ — $ 7.7 $ — $ 507.7 Accounts payable 31.3 — — 1,085.0 — 1,116.3 Other current liabilities 123.2 81.0 — 280.2 — 484.4 Total current liabilities 154.5 581.0 — 1,372.9 — 2,108.4 Intercompany payables — — 7,701.5 6,836.6 (14,538.1 ) — Long-term debt, excluding current maturities 4,510.7 4,341.4 — 21.2 — 8,873.3 Deferred credits and other liabilities Deferred income taxes 112.3 — — 108.4 (1.0 ) 219.7 Other deferred credits 315.6 — — 135.2 — 450.8 Total deferred credits and other liabilities 427.9 — — 243.6 (1.0 ) 670.5 Commitments and contingencies Equity 6,579.5 6,327.2 3,548.1 9,369.8 (19,245.1 ) 6,579.5 Total liabilities and equity $ 11,672.6 $ 11,249.6 $ 11,249.6 $ 17,844.1 $ (33,784.2 ) $ 18,231.7
Condensed Consolidating Statements of Cash Flows	Year Ended December 31, 2019 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 1,010.1 $ 1,332.9 $ 68.9 $ 2,198.9 $ (2,664.0 ) $ 1,946.8 Investing activities Capital expenditures (25.6 ) — — (3,822.7 ) — (3,848.3 ) Other investing activities — — 74.6 4.9 — 79.5 Cash provided by (used in) investing activities (25.6 ) — 74.6 (3,817.8 ) — (3,768.8 ) Financing activities Dividends paid (1,457.6 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (1,457.6 ) Intercompany borrowings (advances), net (3,618.6 ) 801.8 1,188.5 1,628.3 — — Short-term borrowings, net 220.0 — — — — 220.0 Issuance of long-term debt, net of discounts 4,185.4 — — — — 4,185.4 Repayment of long-term debt (249.6 ) (800.0 ) — (7.7 ) — (1,057.3 ) Issuance of common stock 29.0 — — — — 29.0 Other, net (84.1 ) (2.7 ) — (1.7 ) — (88.5 ) Cash provided by (used in) financing activities (975.5 ) (1,332.9 ) (143.5 ) 1,618.9 2,664.0 1,831.0 Change in cash and cash equivalents 9.0 — — — — 9.0 Cash and cash equivalents at beginning of period 12.0 — — — — 12.0 Cash and cash equivalents at end of period $ 21.0 $ — $ — $ — $ — $ 21.0 Year Ended December 31, 2018 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 1,325.1 $ 1,344.7 $ 67.9 $ 2,113.0 $ (2,664.0 ) $ 2,186.7 Investing activities Capital expenditures (18.8 ) — — (2,122.7 ) — (2,141.5 ) Other investing activities — — 15.3 11.3 — 26.6 Cash provided by (used in) investing activities (18.8 ) — 15.3 (2,111.4 ) — (2,114.9 ) Financing activities Dividends paid (1,335.1 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (1,335.1 ) Distributions to noncontrolling interests — — — (3.5 ) — (3.5 ) Intercompany borrowings (advances), net (2,154.4 ) 912.3 1,248.8 (6.7 ) — — Repayment of short-term borrowings, net (614.7 ) — — — — (614.7 ) Issuance of long-term debt, net of discounts 1,795.8 — — — — 1,795.8 Repayment of long-term debt — (925.0 ) — (7.7 ) — (932.7 ) Issuance of common stock 1,204.0 — — — — 1,204.0 Acquisition of noncontrolling interests (195.0 ) — — — — (195.0 ) Other, net (32.1 ) — — 16.3 — (15.8 ) Cash used in financing activities (1,331.5 ) (1,344.7 ) (83.2 ) (1.6 ) 2,664.0 (97.0 ) Change in cash and cash equivalents (25.2 ) — — — — (25.2 ) Cash and cash equivalents at beginning of period 37.2 — — — — 37.2 Cash and cash equivalents at end of period $ 12.0 $ — $ — $ — $ — $ 12.0 Year Ended December 31, 2017 Parent Issuer & Guarantor Subsidiary Issuer & Guarantor Guarantor Subsidiary Combined Non-Guarantor Subsidiaries Consolidating Entries and Other Total ( Millions of dollars ) Operating activities Cash provided by operating activities $ 947.4 $ 1,348.3 $ 59.0 $ 1,353.7 $ (2,393.0 ) $ 1,315.4 Investing activities Capital expenditures — — — (512.4 ) — (512.4 ) Contributions to unconsolidated affiliates — — (83.0 ) (4.9 ) — (87.9 ) Other investing activities — — 14.8 17.9 — 32.7 Cash used in investing activities — — (68.2 ) (499.4 ) — (567.6 ) Financing activities Dividends paid (829.4 ) (1,332.0 ) (1,332.0 ) — 2,664.0 (829.4 ) Distributions to noncontrolling interests — — — (5.3 ) (271.0 ) (276.3 ) Intercompany borrowings (advances), net (2,500.7 ) 2,001.2 1,340.8 (841.3 ) — — Borrowing (repayment) of short-term borrowings, net 614.7 (1,110.3 ) — — — (495.6 ) Issuance of long-term debt, net of discounts 1,190.5 — — — — 1,190.5 Repayment of long-term debt (87.1 ) (900.0 ) — (7.7 ) — (994.8 ) Issuance of common stock 471.4 — — — — 471.4 Other, net (18.1 ) (7.2 ) — — — (25.3 ) Cash provided by (used in) financing activities (1,158.7 ) (1,348.3 ) 8.8 (854.3 ) 2,393.0 (959.5 ) Change in cash and cash equivalents (211.3 ) — (0.4 ) — — (211.7 ) Cash and cash equivalents at beginning of period 248.5 — 0.4 — — 248.9 Cash and cash equivalents at end of period $ 37.2 $ — $ — $ — $ — $ 37.2

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Entity [Line Items]
Equity Method Investment, Ownership Percentage	50.00%
Contract Liabilities, Contract Term	5 to 10 years
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
General partner ownership interest	100.00%
Common stock	$ 29,040	$ 1,203,981	$ 471,358
Noncontrolling interests in consolidated subsidiaries		$ (195,000)	$ 2,146,462
Number Of Years Of Service Employees Must Work To Be Entitled To Postretirement Medical And Life Insurance Benefits			5 years
Accounting Standards Update 2016-02 [Member]
Entity [Line Items]
Finance lease assets - PPE				$ 28,100
Present value of lease liabilities				$ 28,000

FAIR VALUE MEASUREMENTS - Part

FAIR VALUE MEASUREMENTS - Part 1 (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash held - offsetting derivative net asset positions under master-netting arrangements	$ 0	$ 0
Cash posted - total	8,800	800
Cash posted - offsetting derivative net liability positions under master-netting arrangements	0	0
Long-term Debt, Fair Value	13,800,000	9,600,000
Long-term Debt	12,500,000	9,400,000
Fair Value, Recurring [Member]
Derivative assets
Financial contracts	37,861	47,238
Physical contracts		1,142
Interest-rate contracts	581	19,005
Total derivative assets	38,442	67,385
Derivative assets netting	(28,588)	(32,739)
Derivative Liabilities
Financial contracts	(1,008)	0
Interest-rate contracts	(201,941)	(99,260)
Total derivative liabilities	(202,949)	(99,260)
Derivative liabilities netting	28,588	32,739
Fair Value, Recurring [Member] | Gross Fair Value Measurement [Member]
Derivative assets
Financial contracts	66,449	79,977
Physical contracts		1,142
Interest-rate contracts	581	19,005
Total derivative assets	67,030	100,124
Derivative Liabilities
Financial contracts	(29,596)	(32,739)
Interest-rate contracts	(201,941)	(99,260)
Total derivative liabilities	(231,537)	(131,999)
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative assets
Financial contracts	10,892	10,812
Physical contracts		0
Interest-rate contracts	0	0
Total derivative assets	10,892	10,812
Derivative Liabilities
Financial contracts	(4,811)	(2,916)
Interest-rate contracts	0	0
Total derivative liabilities	(4,811)	(2,916)
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative assets
Financial contracts	0	0
Physical contracts		0
Interest-rate contracts	581	19,005
Total derivative assets	581	19,005
Derivative Liabilities
Financial contracts	0	0
Interest-rate contracts	(201,941)	(99,260)
Total derivative liabilities	(201,941)	(99,260)
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative assets
Financial contracts	55,557	69,165
Physical contracts		1,142
Interest-rate contracts	0	0
Total derivative assets	55,557	70,307
Derivative Liabilities
Financial contracts	(24,785)	(29,823)
Interest-rate contracts	0	0
Total derivative liabilities	(24,785)	(29,823)
Interest Rate Contract | Fair Value, Recurring [Member]
Derivative assets
Derivative assets netting	0	0
Derivative Liabilities
Derivative liabilities netting	0	0
Physical Contracts [Member] | Fair Value, Recurring [Member]
Derivative assets
Derivative assets netting		0
Financial contracts | Fair Value, Recurring [Member]
Derivative assets
Derivative assets netting	(28,588)	(32,739)
Derivative Liabilities
Derivative liabilities netting	$ 28,588	$ 32,739

FAIR VALUE MEASUREMENTS - Par_2

FAIR VALUE MEASUREMENTS - Part 2 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets And Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Abstract]
Net assets (liabilities) at beginning of period	$ 40,484	$ (32,838)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	(140)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements	(40,344)	29,141
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, New Level 3 Derivatives	30,627	37,106
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Unrealized Gain (Loss) Included in Other Comprehensive Income (Loss)	5	7,215
Net assets (liabilities) at end of period	30,772	40,484
Transfers in or out of level 3	$ 0	$ 0

RISK MANAGEMENT AND HEDGING A_3

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 1 (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Derivative, Net Liability Position, Aggregate Fair Value	$ 0
Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	67,030,000	$ 100,124,000
(Liabilities)	(231,537,000)	(131,999,000)
Natural Gas Pipelines
Derivatives, Fair Value [Line Items]
Derivative, Fair Value, Net	0	0
Other Current Assets [Member] | Commodity contracts | Financial contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	64,858,000	78,891,000
(Liabilities)	(26,997,000)	(31,793,000)
Other Current Assets [Member] | Commodity contracts | Physical contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	0	1,142,000
(Liabilities)	0	0
Other Current Assets [Member] | Interest Rate Contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	0	19,005,000
Other Current Liabilities [Member] | Interest Rate Contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
(Liabilities)	(90,161,000)	(15,012,000)
Other Assets [Member] | Commodity contracts | Financial contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	1,591,000	1,086,000
Other Assets [Member] | Interest Rate Contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Assets	581,000	0
Other Deferred Credits | Commodity contracts | Financial contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
(Liabilities)	(2,599,000)	(946,000)
Other Deferred Credits | Interest Rate Contracts | Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
(Liabilities)	(111,780,000)	(84,248,000)
Interest Rate Contracts | LIBOR Based Interest Payments [Member] | Cash Flow Hedging [Member] | Forward contracts
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 1,300,000,000	$ 1,300,000,000

RISK MANAGEMENT AND HEDGING A_4

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 2 (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)MMcfMMBbls	Sep. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)MMcfMMBbls
Derivative [Line Items]
Notional Amount Of Cash Flow Hedge Instruments Settled	$ 1,800,000
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Fixed price | Purchased/Payor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMcf	0			0
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Fixed price | Sold/Receiver
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMcf	(59,000)			(29,900)
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Basis | Purchased/Payor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMcf	0			0
Derivatives designated as hedging instruments | Futures and swaps | Natural gas (Bcf) | Basis | Sold/Receiver
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMcf	(59,000)			(29,900)
Derivatives designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Purchased/Payor
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBbls	7.9			6.5
Derivatives designated as hedging instruments | Futures, forwards and swaps | Crude oils and NGLs (MMBbl) | Fixed price | Sold/Receiver
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBbls	(17.4)			(13.8)
Derivatives designated as hedging instruments | Interest Rate Contracts | Purchased/Payor
Derivative [Line Items]
Derivative, Notional Amount	$ 3,100,000			$ 4,300,000
Derivatives designated as hedging instruments | Interest Rate Contracts | Sold/Receiver
Derivative [Line Items]
Derivative, Notional Amount	0			0
LIBOR Based Interest Payments [Member] | Cash Flow Hedging [Member] | Forward contracts | Interest Rate Contracts
Derivative [Line Items]
Derivative, Notional Amount	1,300,000			1,300,000
Forecasted Debt Issuances [Member] | Cash Flow Hedging [Member] | Forward contracts
Derivative [Line Items]
Derivative, Notional Amount, New Contracts	625,000
Forecasted Debt Issuances [Member] | Cash Flow Hedging [Member] | Forward contracts | Interest Rate Contracts
Derivative [Line Items]
Derivative, Notional Amount	1,800,000			$ 3,000,000
Notes Payable from Public Offering Due 2029 and 2048 [Member]
Derivative [Line Items]
Senior Notes, Noncurrent	1,250,000		$ 1,250,000
Notes Payable from Public Offering Due 2024, 2029 and 2049 [Member]
Derivative [Line Items]
Senior Notes, Noncurrent	$ 2,000,000	$ 2,000,000

RISK MANAGEMENT AND HEDGING A_5

RISK MANAGEMENT AND HEDGING ACTIVITIES USING DERIVATIVES - Part 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income	$ 27,115	$ (47,883)	$ (90,586)
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	(191,952)	(7,367)	(40,414)
Commodity contracts | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	38,819	53,217	(40,577)
Commodity contracts | Commodity sales revenues / cost of sales and fuel | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income	50,345	(29,596)	(69,561)
Interest Rate Contracts | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized change in fair value of cash flow hedges in other comprehensive income (loss)	(230,771)	(60,584)	163
Interest Rate Contracts | Interest expense | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income	(23,230)	(18,287)	(21,025)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Commodity contracts | Commodity sales revenues / cost of sales and fuel
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income	50,345	(29,596)	(69,561)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Rate Contracts | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Change in fair value of cash flow hedges reclassified from accumulated other comprehensive loss into net income	$ (23,230)	$ (18,287)	$ (21,025)

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 22,051,492	$ 18,030,963
Accumulated depreciation and amortization	(3,702,807)	(3,264,312)
Net property, plant and equipment	18,348,685	14,766,651
Construction in Progress Expenditures Incurred but Not yet Paid	544,800	388,300	$ 92,400
Impairment of long-lived assets	0	0	$ 15,970
Non-Regulated Property, Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	(2,471,649)	(2,168,855)
Non-Regulated Property, Plant and Equipment [Member] | Gathering pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 4,316,936	3,851,043
Non-Regulated Property, Plant and Equipment [Member] | Gathering pipelines and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Non-Regulated Property, Plant and Equipment [Member] | Gathering pipelines and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Non-Regulated Property, Plant and Equipment [Member] | Processing and fractionation and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 4,439,332	4,171,072
Non-Regulated Property, Plant and Equipment [Member] | Processing and fractionation and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Non-Regulated Property, Plant and Equipment [Member] | Processing and fractionation and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Non-Regulated Property, Plant and Equipment [Member] | Storage and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 684,635	656,455
Non-Regulated Property, Plant and Equipment [Member] | Storage and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Non-Regulated Property, Plant and Equipment [Member] | Storage and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	54 years
Non-Regulated Property, Plant and Equipment [Member] | Transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 797,678	782,258
Non-Regulated Property, Plant and Equipment [Member] | Transmission pipelines and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Non-Regulated Property, Plant and Equipment [Member] | Transmission pipelines and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	54 years
Non-Regulated Property, Plant and Equipment [Member] | General plant and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 610,013	547,424
Non-Regulated Property, Plant and Equipment [Member] | General plant and other | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Non-Regulated Property, Plant and Equipment [Member] | General plant and other | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	60 years
Non-Regulated Property, Plant and Equipment [Member] | Construction work in process
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 1,645,663	797,182
Regulated Property Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (1,231,158)	$ (1,095,457)
Regulated Property Plant and Equipment [Member] | Natural Gas Liquids
Property, Plant and Equipment [Line Items]
Average Depreciation Rate	2.00%	1.90%	1.90%
Regulated Property Plant and Equipment [Member] | Natural Gas Pipelines
Property, Plant and Equipment [Line Items]
Average Depreciation Rate	2.10%	2.10%	2.10%
Regulated Property Plant and Equipment [Member] | Storage and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 9,180	$ 8,987
Regulated Property Plant and Equipment [Member] | Storage and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] | Storage and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	25 years
Regulated Property Plant and Equipment [Member] | General plant and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 66,507	61,136
Regulated Property Plant and Equipment [Member] | General plant and other | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Regulated Property Plant and Equipment [Member] | General plant and other | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	50 years
Regulated Property Plant and Equipment [Member] | Construction work in process
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 1,802,946	1,002,018
Regulated Property Plant and Equipment [Member] | Natural gas transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 1,552,546	1,475,789
Regulated Property Plant and Equipment [Member] | Natural gas transmission pipelines and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] | Natural gas transmission pipelines and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	77 years
Regulated Property Plant and Equipment [Member] | NGL transmission pipelines and related equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment	$ 6,126,056	$ 4,677,599
Regulated Property Plant and Equipment [Member] | NGL transmission pipelines and related equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Regulated Property Plant and Equipment [Member] | NGL transmission pipelines and related equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	88 years

GOODWILL AND INTANGIBLE ASSET_3

GOODWILL AND INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Goodwill	$ 680,996	$ 681,100
Amortization expense for intangible assets	11,900	11,900	$ 11,900
Gross intangible assets and accumulated amortization [Abstract]
Gross intangible assets	414,345	411,650
Accumulated amortization	(137,508)	(125,608)
Net intangible assets	276,837	286,042
Future amortization expense for next five years [Abstract]
Future amortization expense, year one	11,900
Future amortization expense, year two	11,900
Future amortization expense, year three	11,900
Future amortization expense, year four	11,900
Future amortization expense, year five	$ 11,900
Natural Gas Gathering And Processing and Natural Gas Liquids [Member] | Minimum [Member]
Segment Reporting Information [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Natural Gas Gathering And Processing and Natural Gas Liquids [Member] | Maximum [Member]
Segment Reporting Information [Line Items]
Finite-Lived Intangible Asset, Useful Life	40 years
Natural Gas Gathering and Processing
Segment Reporting Information [Line Items]
Goodwill	$ 153,404	153,404
Natural Gas Liquids
Segment Reporting Information [Line Items]
Goodwill	371,217	371,217
Natural Gas Pipelines
Segment Reporting Information [Line Items]
Goodwill	$ 156,375	$ 156,479

DEBT (Details)

DEBT (Details) $ in Thousands	3 Months Ended	9 Months Ended			12 Months Ended
	Mar. 31, 2019USD ($)Rate	Sep. 30, 2019USD ($)Rate	Sep. 30, 2018USD ($)Rate	Sep. 30, 2017USD ($)Rate	Dec. 31, 2019USD ($)Rate	Dec. 31, 2018USD ($)Rate
Debt Instrument [Line Items]
Total debt					$ 12,813,704	$ 9,451,354
Unamortized portion of terminated swaps					(15,032)	(16,750)
Unamortized debt issuance costs and discounts					(121,329)	(87,120)
Current maturities of long-term debt					(7,650)	(507,650)
Short-term borrowings					(220,000)	0
Long-term debt					12,479,757	8,873,334
Letters of Credit Outstanding, Amount					4,700	1,400
Senior Note Covenant, Acceleration Of Indebtedness					$ 100,000
Senior Note Covenant, Trustee Or Holders Percentage Required Upon Event Of Default					25.00%
Long-term Debt, by Maturity [Abstract]
2020					$ 7,700
2021					1,257,700
2022					1,453,300
2023					925,000
2024					500,000
$2.5 Billion Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					2,500,000
Line of Credit Facility, Amount Outstanding					$ 0	0
Indebtedness to Adjusted EBITDA Maximum					5
Indebtedness To Adjusted EBITDA From Acquisitions Maximum					5.5
Aggregate Purchase Price For Acquisitions Threshold Which Adjusts Allowable Ratio Of Indebtedness To Adjusted EBITDA					$ 25,000
Line of Credit Facility, Sublimit					100,000
Line of Credit Facility, Swingline Subfacility					200,000
Line Of Credit Facility, Option To Increase Borrowing Capacity					$ 3,500,000
Line of Credit Facility, Annual Facility Fee					0.15%
Indebtedness To Adjusted EBITDA Current					4.1
Debt Instrument, Covenant Description					Among other things, these covenants include maintaining a ratio of indebtedness to adjusted EBITDA (EBITDA, as defined in our $2.5 Billion Credit Agreement, adjusted for all noncash charges and increased for projected EBITDA from certain lender-approved capital expansion projects) of no more than 5.0 to 1 at December 31, 2019. If we consummate one or more acquisitions in which the aggregate purchase is $25 million or more, the allowable ratio of indebtedness to adjusted EBITDA will increase to 5.5 to 1 for the quarter in which the acquisition is completed and the following two quarters. Thereafter, the covenant will decrease to 5.0 to 1. Our $2.5 Billion Credit Agreement includes a $100 million sublimit for the issuance of standby letters of credit and a $200 million sublimit for swingline loans. Under the terms of our $2.5 Billion Credit Agreement, we may request an increase in the size of the facility to an aggregate of $3.5 billion by either commitments from new lenders or increased commitments from existing lenders. Our $2.5 Billion Credit Agreement contains provisions for an applicable margin rate and an annual facility fee, both of which adjust with changes in our credit ratings. Based on our current credit ratings, borrowings, if any, will accrue at LIBOR plus 110 basis points, and the annual facility fee is 15 basis points. At December 31, 2019, our ratio of indebtedness to adjusted EBITDA was 4.1 to 1, and we were in compliance with all covenants under our $2.5 Billion Credit Agreement.
Notes Payable from Public Offering Due 2024, 2029 and 2049 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent		$ 2,000,000			$ 2,000,000
Proceeds from Debt, Net of Issuance Costs		1,970,000
Notes Payable from Public Offering Due 2029 and 2048 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent	$ 1,250,000				1,250,000
Proceeds from Debt, Net of Issuance Costs	1,230,000
Notes Payable from Public Offering Due 2028 and 2048 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent			$ 1,250,000
Proceeds from Debt, Net of Issuance Costs			1,230,000
Notes Payable from Public Offering Due 2027 and 2047 [Member]
Debt Instrument [Line Items]
Senior Notes, Noncurrent				$ 1,200,000
Proceeds from Debt, Net of Issuance Costs				1,200,000
Senior Notes [Member]
Long-term Debt, by Maturity [Abstract]
2020					0
2021					1,250,000
2022					1,447,400
2023					925,000
2024					$ 500,000
Guardian Pipeline [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description					Guardian Pipeline’s senior notes contain financial covenants that require the maintenance of certain financial ratios as defined in the master shelf agreement based on Guardian Pipeline’s financial position and results of operations. Upon any breach of these covenants, all amounts outstanding under the master shelf agreement may become due and payable immediately
Debt Instrument, Covenant Compliance					At December 31, 2019, Guardian Pipeline was in compliance with its financial covenants
Guardian Pipeline [Member] | Notes Payables 1 due 2022 [Member]
Debt Instrument [Line Items]
Total debt					$ 21,307	28,957
Average interest rate (in hundredths) | Rate					7.85%
Long-term Debt, by Maturity [Abstract]
2020					$ 7,700
2021					7,700
2022					5,900
2023					0
2024					0
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2017 [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 400,000
Interest rates (in hundredths) | Rate				2.00%
Subsidiary Issuer [Member] | Term Loan Agreement due 2019 [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			500,000	$ 500,000
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2023 [Member]
Debt Instrument [Line Items]
Total debt					$ 425,000	425,000
Interest rates (in hundredths) | Rate					5.00%
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2025 [Member]
Debt Instrument [Line Items]
Total debt					$ 500,000	500,000
Interest rates (in hundredths) | Rate					4.90%
Subsidiary Issuer [Member] | Notes Payables due 2036 [Member]
Debt Instrument [Line Items]
Total debt					$ 600,000	600,000
Interest rates (in hundredths) | Rate					6.65%
Subsidiary Issuer [Member] | Notes Payables due 2037 [Member]
Debt Instrument [Line Items]
Total debt					$ 600,000	600,000
Interest rates (in hundredths) | Rate					6.85%
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2041 [Member]
Debt Instrument [Line Items]
Total debt					$ 650,000	650,000
Interest rates (in hundredths) | Rate					6.125%
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2043 [Member]
Debt Instrument [Line Items]
Total debt					$ 400,000	400,000
Interest rates (in hundredths) | Rate					6.20%
Subsidiary Issuer [Member] | Notes Payables due 2019 [Member]
Debt Instrument [Line Items]
Total debt					$ 0	500,000
Repayments of Long-term Debt	$ 500,000
Interest rates (in hundredths) | Rate	8.625%				8.625%
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2018 [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 425,000
Interest rates (in hundredths) | Rate			3.20%
Subsidiary Issuer [Member] | Note Payable from Public Offering Due 2020 [Member]
Debt Instrument [Line Items]
Total debt					$ 0	300,000
Extinguishment of Debt, Amount		$ 300,000
Interest rates (in hundredths) | Rate		3.80%			3.80%
Long-term Debt, by Maturity [Abstract]
Debt Instrument, Redemption Price		$ 308,000
Gain (Loss) on Extinguishment of Debt		(2,700)
Subsidiary Issuer [Member] | Note Payable 2 from Public Offering Due 2022 [Member]
Debt Instrument [Line Items]
Total debt					$ 900,000	900,000
Interest rates (in hundredths) | Rate					3.375%
Parent Company
Debt Instrument [Line Items]
Commercial Paper					$ 220,000	$ 0
Short-term Debt, Weighted Average Interest Rate, at Point in Time | Rate					2.16%	0.00%
Parent Company | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Description					Our senior notes are governed by indentures containing covenants, including among other provisions, limitations on our ability to place liens on our property or assets and to sell and leaseback our property. The indentures governing our 6.875% senior notes due 2028 include an event of default upon acceleration of other indebtedness of $15 million or more, and the indentures governing the remainder of our senior notes include an event of default upon the acceleration of other indebtedness of $100 million or more. Such events of default would entitle the trustee or the holders of 25% in aggregate principal amount of the outstanding senior notes to declare those senior notes immediately due and payable in full. The indenture for the 7.5% notes due 2023 also contains a provision that allows the holders of the notes to require ONEOK to offer to repurchase all or any part of their notes if a change of control and a credit rating downgrade occur at a purchase price of 101% of the principal amount, plus accrued and unpaid interest, if any.
Debt instrument call feature					We may redeem our senior notes, in whole or in part, at any time prior to their maturity at a redemption price equal to the principal amount, plus accrued and unpaid interest and a make-whole premium. We may redeem the balance of our senior notes due 2022, 2023, 2024, 2025, 2027, 2028 (4.55%), 2029, 2041, 2043, 2047, 2048 and 2049 at a redemption price equal to the principal amount, plus accrued and unpaid interest, starting one to six months before the maturity date as stipulated in the respective contract terms. Our senior notes are senior unsecured obligations, ranking equally in right of payment with all of our existing and future unsecured senior indebtedness.
Parent Company | Term Loan Agreement due 2021 [Member]
Debt Instrument [Line Items]
Total debt					$ 1,250,000	$ 550,000
Debt Instrument, Face Amount					1,500,000
Repayments of Long-term Debt		250,000
Parent Company | Note Payable from Public Offering Due 2022 [Member]
Debt Instrument [Line Items]
Total debt					$ 547,397	547,397
Interest rates (in hundredths) | Rate					4.25%
Parent Company | Note Payable Due 2023 [Member]
Debt Instrument [Line Items]
Total debt					$ 500,000	500,000
Interest rates (in hundredths) | Rate					7.50%
Senior Note Covenant, Redemption Price Upon Event Of Default | Rate					101.00%
Parent Company | Note Payable Due 2024 [Member]
Debt Instrument [Line Items]
Total debt		$ 500,000			$ 500,000	0
Interest rates (in hundredths) | Rate		2.75%			2.75%
Parent Company | Note Payable Due 2027 [Member]
Debt Instrument [Line Items]
Total debt				$ 500,000	$ 500,000	500,000
Interest rates (in hundredths) | Rate				4.00%	4.00%
Parent Company | Note Payables 1 due 2028 [Member]
Debt Instrument [Line Items]
Total debt			$ 800,000		$ 800,000	800,000
Interest rates (in hundredths) | Rate			4.55%		4.55%
Parent Company | Note Payables 2 due 2028 [Member]
Debt Instrument [Line Items]
Total debt					$ 100,000	100,000
Interest rates (in hundredths) | Rate					6.875%
Senior Note Covenant, Acceleration Of Indebtedness					$ 15,000
Parent Company | Note Payable from Public Offering Due 2029 [Member]
Debt Instrument [Line Items]
Total debt	$ 700,000				$ 700,000	0
Interest rates (in hundredths) | Rate	4.35%				4.35%
Parent Company | Note Payables, Additional Issuance, due 2048 [Member]
Debt Instrument [Line Items]
Total debt	$ 550,000
Interest rates (in hundredths) | Rate	5.20%
Parent Company | Note Payable Due 2029 [Member]
Debt Instrument [Line Items]
Total debt		$ 750,000			$ 750,000	0
Interest rates (in hundredths) | Rate		3.40%			3.40%
Parent Company | Notes Payables due 2035 [Member]
Debt Instrument [Line Items]
Total debt					$ 400,000	400,000
Interest rates (in hundredths) | Rate					6.00%
Parent Company | Notes Payables due 2047 [Member]
Debt Instrument [Line Items]
Total debt				$ 700,000	$ 700,000	700,000
Interest rates (in hundredths) | Rate				4.95%	4.95%
Parent Company | Note Payable from Public Offering Due 2047 [Member]
Debt Instrument [Line Items]
Interest rates (in hundredths) | Rate			5.20%
Parent Company | Note Payables due 2048 [Member]
Debt Instrument [Line Items]
Total debt			$ 450,000		$ 1,000,000	450,000
Interest rates (in hundredths) | Rate					5.20%
Parent Company | Note Payable Due 2049 [Member]
Debt Instrument [Line Items]
Total debt		$ 750,000			$ 750,000	$ 0
Interest rates (in hundredths) | Rate		4.45%			4.45%
Parent Company | Term Loan Agreement due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate | Rate					2.70%	3.63%
Parent Company | Note Payable from Public Offering Due 2028 [Member]
Debt Instrument [Line Items]
Interest rates (in hundredths) | Rate				6.50%
Long-term Debt, by Maturity [Abstract]
Debt Instrument, Redemption Price				$ 87,000
London Interbank Offered Rate (LIBOR) [Member] | $2.5 Billion Credit Agreement [Member]
Long-term Debt, by Maturity [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.10%
London Interbank Offered Rate (LIBOR) [Member] | Parent Company | Term Loan Agreement due 2021 [Member]
Long-term Debt, by Maturity [Abstract]
Debt Instrument, Basis Spread on Variable Rate					1.125%

EQUITY EQUITY (Details)

EQUITY EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended													12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
General partner ownership interest														100.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners								20.00%
Business Combination, Consideration Transferred							$ 195,000
Common Stock, Dividends, Per Share, Cash Paid		$ 0.915	$ 0.890	$ 0.865	$ 0.860	$ 0.855	$ 0.825	$ 0.795	$ 0.770	$ 0.745	$ 0.745	$ 0.615	$ 0.615	$ 3.53	$ 3.245	$ 2.72
Dividends, Cash														$ 1,500,000	$ 1,300,000	$ 829,400
Public Offering Price of Common Stock									$ 54.50
Stock Issued During Period, Shares, New Issues									21,900,000
Noncash Contribution Expense														0	0	12,600
Dividends, Preferred Stock, Cash														1,100	1,100	600
Preferred stock dividends paid														$ 1,100	$ 1,100	$ 767
Proceeds from Issuance or Sale of Equity									$ 1,200,000
Issued Under Equity Agreement
Common Stock Sold Under Equity Distribution Agreement														0	0
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared, Annualized	$ 3.74
Common Stock, Dividends, Per Share, Declared	$ 0.935
Preferred stock dividends paid	$ 300
Dividends Payable, Date to be Paid	Jan. 27, 2020
Issued Under Equity Agreement
Common Stock Sold Under Equity Distribution Agreement																8,400,000
Proceeds from Issuance or Sale of Equity																$ 448,300
Series A Preferred Stock [Member]
Preferred Stock, Shares Outstanding		0												0
Series B Preferred Stock [Member]
Preferred Stock, Shares Outstanding		0												0
Series E Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues												20,000
Stock Issued During Period, Value, New Issues												$ 20,000
Noncash Contribution Expense												$ 20,000				$ 20,000
Preferred Stock, Dividend Rate, Percentage														5.50%
ONEOK
Aggregate Amount Of Common Shares Available For Issuance And Sale Under Equity Distribution Agreement											$ 1,000,000

ACCUMULATED OTHER COMPREHENSI_3

ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive (Income) Loss Before Reclassification, Retirement and Other Postretirement Benefit Plan Obligations	$ (19,490)	$ (8,116)
Other Comprehensive Income (Loss) Before Reclassification, Risk-Management Assets/Liabilities of Unconsolidated Affiliates	(7,275)	2,396
Other comprehensive income (loss) before reclassifications	(174,568)	(11,393)
Other Comprehensive Income (Loss), Risk-Management Assets/Liabilities, after Reclassification Adjustment, after Tax	(168,860)
Change in fair value of derivatives, net of tax	(147,803)	(5,673)	$ (21,408)
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(21,057)	36,870	63,687
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)
Other comprehensive Income (Loss), Reclassification Adjustment included in Net Income, Net of Tax	(11,193)	49,785	53,867
Other Comprehensive Income (Loss), Risk-management Assets/Liabilities, after Reclassification, Adjustment, Net of Tax, Portion Attributable to Parent		31,197
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, after Reclassification Adjustment, after Tax	(9,696)	4,771	(4,175)
Other comprehensive income (loss) Risk-Management Assets/Liabilities of unconsolidated affiliates	(7,205)	2,424	(970)
Other Comprehensive Income (Loss), Net of Tax	(185,761)	38,392	37,134
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		38,392
Impact of Adoption of ASU 2018-02 on Unrealized Gains (Losses) on Risk Management Assets/Liabilities		(17,020)
Impact of Adoption of ASU 2018-02 on Retirement and Other Postretirement Benefit Plan Obligations		(20,340)
Impact of Adoption of ASU 2018-02 on Unrealized Gains (Losses) on Risk Management Assets/Liabilities of Unconsolidated Affiliates		(741)
Impact of Adoption of ASU 2018-02 on AOCI, Total		(38,101)
Risk management assets/liabilities - December 31	(233,520)	(64,660)	(81,915)
Retirement and Other Postretirement Benefit Plan Obligations - December 31	(131,481)	(121,785)	(105,411)
Risk-management assets/liabilities of unconsolidated affiliates - December 31	(8,999)	(1,794)	(1,204)
Accumulated other comprehensive loss - December 31	(374,000)	(188,239)	(188,530)
Beginning balance adjustments on Risk management assets/liabilities			3,078
Beginning balance adjustments on retirement and other postretirement benefit plan obligations			(805)
Beginning balance adjustments on risk-management asset/liabilities of unconsolidated affiliates			(2,273)
Beginning balance adjustments on accumulated other comprehensive loss			0
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(6,058)	11,013	26,899
Price Risk Cash Flow Hedge Unrealized Gain (Loss) to be Reclassified During Next 12 Months	28,900
Commodity Cash Flow Hedge Gain (Loss) To Be Reclassified After Next 12 Months Net	(800)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	(20,300)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax			45,541
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	50,345	(29,596)	(69,561)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Interest Expense [Member] | Interest Rate Contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	(23,230)	(18,287)	(21,025)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Total before tax [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	27,115	(47,883)	(90,586)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Tax Expense [Member]
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities, Income Tax	(6,058)	11,013	26,899
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Net of tax [Member]
Other comprehensive Income (Loss) Reclassification Adjustment from AOCI for Risk-Management Assets/Liabilities, Net of Tax	(21,057)	36,870	63,687
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Net income attributable to noncontrolling interest [Member]
Reclassification Adjustment from AOCI on Risk Management Assets/Liabilities Net of Tax, Portion Attributable to Noncontrolling Interest	0	0	(18,146)
Accumulated Retirement and Other Postretirement Benefit Plans Adjustment Attributable to Parent [Member]
Other Comprehensive (Income) Loss, Retirement and Other Postretirement Benefit Plans, Reclassification Adjustment from AOCI, After Tax	(9,794)	(12,887)	(8,162)
Retirement and Other Postretirement Benefit Plans, Amortization of Gain (Loss)	(12,946)	(18,398)	(15,265)
Retirement and Other Postretirement Benefit Plans, Amortization of Prior Service Credit	227	1,662	1,662
Reclassification Adjustment from AOCI, before Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	(12,719)	(16,736)	(13,603)
Reclassification Adjustment from AOCI, Tax, Retirement and Other Postretirement Benefit Plans, Gain (Loss)	2,925	3,849	5,441
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates Attributable to Parent [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)	(164)
Reclassification Adjustment from AOCI, Before Tax, Portion Attributable to Unconsolidated Affiliates	(91)	(36)	(367)
Reclassification Adjustment from AOCI, Tax, Portion Attributable to Unconsolidated Affiliates	21	8	97
Accumulated Other Comprehensive Income from Investments in Unconsolidated Affiliates Attributable to Parent [Member] | Net of tax [Member]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Other Comprehensive Income Attributable to Unconsolidated Affiliates, Net of Tax	(70)	(28)	(270)
Reclassification Adjustment from AOCI, Net of Tax, Portion Attributable to Noncontrolling Interests	0	0	(106)
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax	(185,761)	38,392	6,108
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	27,115	(47,883)	(90,586)
Cash Flow Hedging [Member] | Commodity Contract [Member]
Unrealized Gain Loss On Cash Flow Hedges Net Of Tax Accumulated Other Comprehensive Income Loss	28,119
Cash Flow Hedging [Member] | Interest Rate Contracts
Amount of accumulated other comprehensive income (loss) attributable primarily to settled interest-rate swaps.	(106,592)
Cash Flow Hedging [Member] | Forward Contracts [Member]
Amount of accumulated other comprehensive income (loss) attributable primarily to forward starting interest-rate swaps.	(155,047)
Cash Flow Hedging [Member] | Sales [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	50,345	(29,596)	(69,561)
Cash Flow Hedging [Member] | Interest Expense [Member] | Interest Rate Contracts
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income	$ (23,230)	$ (18,287)	$ (21,025)

EARNINGS PER SHARE EARNINGS P_3

EARNINGS PER SHARE EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic EPS
Net income available for common stock	$ 319,976	$ 308,880	$ 311,688	$ 336,933	$ 292,613	$ 312,984	$ 280,773	$ 264,233	$ 1,277,477	$ 1,150,603	$ 387,074
Shares									413,560	411,485	297,477
Basic	$ 0.77	$ 0.75	$ 0.75	$ 0.82	$ 0.71	$ 0.76	$ 0.68	$ 0.65	$ 3.09	$ 2.80	$ 1.30
Diluted EPS
Effect of dilutive securities									$ 0	$ 0	$ 0
Effect of dilutive securities, number of shares									1,884	2,710	2,303
Net income available for common stock and common stock equivalents									$ 1,277,477	$ 1,150,603	$ 387,074
Shares									415,444	414,195	299,780
Diluted	$ 0.77	$ 0.74	$ 0.75	$ 0.81	$ 0.70	$ 0.75	$ 0.68	$ 0.64	$ 3.07	$ 2.78	$ 1.29

SHARE-BASED PAYMENTS SHARE-BA_3

SHARE-BASED PAYMENTS SHARE-BASED PAYMENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	8,500,000
Number of Shares Available for Grant	7,600,000
Maximum Value of Shares For Which Awards May Be Issued To A Participant During Any Year	$ 800
Forfeiture rate maximum (in hundredths)	3.00%
Allocated share-based compensation expense	$ 46,500	$ 33,200	$ 27,700
Tax Benefit	$ 31,700	$ 12,200	$ 11,100
Performance Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period	3 years
Nonvested Award, Cost Not yet Recognized, Amount	$ 23,500
Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 9 months 18 days
Nonvested, number of units	937,821	1,243,643
Granted, units	338,427
Released to participants, units	(636,628)
Forfeited, units	(7,621)
Nonvested, Weighted Average Grant Date Fair Value	$ 66.67	$ 44.08
Grants in Period, Weighted Average Grant Date Fair Value	68.02	$ 59.57	$ 56.65
Vested in Period, Weighted Average Grant Date Fair Value	23.59
Forfeitures, Weighted Average Grant Date Fair Value	$ 39.54
Granted in Period, Fair Value	$ 23,020	$ 22,081	$ 17,621
Vested in Period, Fair Value	$ 15,018	$ 12,545	$ 8,704
Expected Volatility Rate	27.10%	39.20%	40.59%
Expected Dividend Rate	5.05%	5.49%	4.68%
Risk Free Interest Rate	2.47%	2.44%	1.49%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period	3 years
Nonvested Award, Cost Not yet Recognized, Amount	$ 15,400
Nonvested Award, Cost Not yet Recognized, Period for Recognition	1 year 9 months 18 days
Nonvested, number of units	698,990	1,025,193
Granted, units	262,399
Released to participants, units	(541,871)
Forfeited, units	(46,731)
Nonvested, Weighted Average Grant Date Fair Value	$ 54.05	$ 34.68
Grants in Period, Weighted Average Grant Date Fair Value	58.07	$ 46.94	$ 45.11
Vested in Period, Weighted Average Grant Date Fair Value	19.73
Forfeitures, Weighted Average Grant Date Fair Value	$ 49.61
Granted in Period, Fair Value	$ 15,238	$ 13,907	$ 12,685
Vested in Period, Fair Value	$ 10,691	$ 9,552	$ 7,258
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	11,600,000
Maximum allowable percentage of annual base pay withheld to purchase our common stock	10.00%
Purchase price percentage of the lower of its grant date or exercise date market price	85.00%
Employee participation in the plan (in hundredths)	62.00%	60.00%	58.00%
Shares sold under the Employee Stock Purchase Plan	171,590	165,877	151,803
Share Price of Shares Sold Under the Employee Stock Purchase Plan (In Dollars per Share)	$ 51.24	$ 45.53	$ 44.20
Employee Stock Award Program [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Description	Under our Employee Stock Award Program, we issued, for no monetary consideration, to all eligible employees one share of our common stock when the per-share closing price of our common stock on the NYSE was for the first time at or above $13 per share, and one additional share of common stock when the per-share closing price of our common stock on the NYSE was at or above each one dollar increment above $13.
Common Stock, Capital Shares Reserved for Future Issuance	900,000
Allocated share-based compensation expense	$ 1,000	$ 200
Shares Awarded Under Employee Stock Award Program	14,022	2,553	0
Non-employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options, Outstanding, Number	0
Non-employees and Directors [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, units	0

EMPLOYEE BENEFIT PLANS EMPLOY_4

EMPLOYEE BENEFIT PLANS EMPLOYEE BENEFIT PLANS (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Deferred income taxes (a)		$ 2,910	$ (1,425)	$ (878)
Total recognized in other comprehensive income (loss)		(9,696)	4,771	(4,175)
Other Comprehensive Income (Loss), Risk-Management Assets/Liabilities of unconsolidated affiliates			2,424
Accumulated other comprehensive loss, net of tax		$ (131,481)	$ (121,785)	$ (105,411)
Expected long-term return on plan assets		7.50%	8.00%	7.75%
Compensation increase rate		3.65%	3.00%	3.10%
Defined Benefit Plan, Assumptions Used in Calculation (Long-term rate of return and discount rate)		We determine our overall expected long-term rate of return on plan assets based on our review of historical returns and economic growth models. We determine our discount rates annually utilizing portfolios of high quality bonds matched to the estimated benefit cash flows of our retirement and other postretirement benefit plans. Bonds selected to be included in the portfolios are only those rated by S&P or Moody’s as an AA or Aa2 rating or better and exclude callable bonds, bonds with less than a minimum issue size, yield outliers and other filtering criteria to remove unsuitable bonds..
Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit Obligation		$ 534,849	$ 466,994	$ 481,615
Service cost		7,825	7,339	6,896
Interest cost		20,528	17,659	18,645
Plan participants’ contributions		0	0
Actuarial loss (gain)		55,954	(24,345)
Benefits paid		(16,452)	(15,274)
Fair value of plan assets		346,792	290,684	306,008
Actual return on plan assets		58,060	(12,350)
Employer contributions		14,500	12,300
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		0	0
Defined Benefit Plan, Plan Assets, Benefits Paid		16,452	15,274
Balance at December 31		(188,057)	(176,310)
Current liabilities		(4,616)	(4,514)
Noncurrent liabilities		(183,441)	(171,796)
Balance at December 31		(188,057)	(176,310)
Defined Benefit Plan, Accumulated Benefit Obligation		498,800	434,400
Expected return on plan assets		(23,600)	(23,917)	(21,376)
Amortization of prior service credit		0	0	0
Amortization of net loss		12,649	17,060	13,586
Net periodic benefit cost		17,402	18,141	17,751
Net gain (loss)		(25,389)	(16,351)	(16,572)
Prior service cost		(601)	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		12,649	17,060	13,586
Deferred income taxes (a)		3,068	(18,928)	(960)
Total recognized in other comprehensive income (loss)		(10,273)	(18,219)	$ (3,946)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		(601)	0
Accumulated loss		(172,952)	(160,212)
Accumulated other comprehensive loss		(173,553)	(160,212)
Deferred income taxes		46,354	43,286
Accumulated other comprehensive loss, net of tax		$ (127,199)	$ (116,926)
Discount rate		3.50%	4.50%
Compensation increase rate		3.70%	3.65%
Discount Rates - Retirement and Other Postretirement Plans		4.50%	3.75%	4.50%
Domestic and international equities		42.00%
Long duration fixed income		30.00%
Return-seeking credit		11.00%
Hedge funds		10.00%
Real estate funds		7.00%
Total		100.00%
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		$ 18,277
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		19,252
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		20,202
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		21,170
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		22,228
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		123,959
Retirement Plan [Member] | Subsequent Event [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 12,100
Retirement Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		110	$ 153
Retirement Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,263	3,961
Retirement Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,373	4,114
Retirement Plan [Member] | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		343,419	286,570
Retirement Plan [Member] | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		346,792	290,684
Retirement Plan [Member] | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		47	58
Retirement Plan [Member] | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Equity securities | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		47	58
Retirement Plan [Member] | Equity securities | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		149,985	116,790
Retirement Plan [Member] | Equity securities | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		150,032	116,848
Retirement Plan [Member] | Real Estate Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Real Estate Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Real Estate Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Real Estate Funds [Member] | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Real Estate Funds [Member] | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		23,885	20,569
Retirement Plan [Member] | Real Estate Funds [Member] | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		23,885	20,569
Retirement Plan [Member] | Government obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Government obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Government obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Government obligations | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Government obligations | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		50,708	48,913
Retirement Plan [Member] | Government obligations | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		50,708	48,913
Retirement Plan [Member] | Corporate obligations | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Corporate obligations | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Corporate obligations | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Corporate obligations | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Corporate obligations | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		85,898	69,377
Retirement Plan [Member] | Corporate obligations | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		85,898	69,377
Retirement Plan [Member] | Common/collective trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Common/collective trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,263	3,961
Retirement Plan [Member] | Common/collective trusts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Common/collective trusts | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,263	3,961
Retirement Plan [Member] | Common/collective trusts | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Common/collective trusts | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,263	3,961
Retirement Plan [Member] | Money market funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			95
Retirement Plan [Member] | Money market funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] | Money market funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] | Money market funds | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			95
Retirement Plan [Member] | Money market funds | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Retirement Plan [Member] | Money market funds | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			95
Retirement Plan [Member] | Other Investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Other Investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Other Investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Other Investments | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Retirement Plan [Member] | Other Investments | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		32,943	30,921
Retirement Plan [Member] | Other Investments | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		32,943	30,921
Unfunded Capital Commitments		0	$ 0
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		63
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Subtotal
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		63
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Measured at NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Retirement Plan [Member] | Cash and Cash Equivalents [Member] | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 63
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumed Health Care Cost Trend Rate		7.00%	6.50%
Defined Benefit Plan Assumed Ultimate Health Care Cost Trend Rate		5.00%	5.00%
Minimum Number Of Years Of Service For Certain Employees To Be Eligible To Participate In Welfare Plans That Provide Postretirement Medical And Life Insurance Benefits		5 years
Benefit Obligation		$ 52,309	$ 46,840	$ 57,938
Service cost		468	845	662
Interest cost		2,038	2,108	2,261
Plan participants’ contributions		1,142	1,050
Actuarial loss (gain)		5,101	(10,233)
Benefits paid		(3,280)	(4,868)
Fair value of plan assets		39,060	30,800	34,133
Actual return on plan assets		8,087	(998)
Employer contributions		2,000	1,100
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant		1,142	1,050
Defined Benefit Plan, Plan Assets, Benefits Paid		2,969	4,485
Balance at December 31		(13,249)	(16,040)
Current liabilities		0	0
Noncurrent liabilities		(13,249)	(16,040)
Balance at December 31		(13,249)	(16,040)
Expected return on plan assets		(2,285)	(2,690)	(2,257)
Amortization of prior service credit		(227)	(1,662)	(1,662)
Amortization of net loss		297	1,338	1,679
Net periodic benefit cost		291	(61)	683
Net gain (loss)		700	6,545	(328)
Prior service cost		0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		(227)	(1,662)	(1,662)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		297	1,338	1,679
Deferred income taxes (a)		(177)	(2,831)	82
Total recognized in other comprehensive income (loss)		593	3,390	$ (229)
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax		0	227
Accumulated loss		(4,110)	(5,108)
Accumulated other comprehensive loss		(4,110)	(4,881)
Deferred income taxes		1,389	1,567
Accumulated other comprehensive loss, net of tax		$ (2,721)	$ (3,314)
Discount rate		3.50%	4.50%
Discount Rates - Retirement and Other Postretirement Plans		4.50%	3.75%	4.25%
Year that the rate reaches the ultimate trend rate		2024	2022
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year		$ 2,000
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months		3,422
Defined Benefit Plan, Expected Future Benefit Payment, Year Two		3,399
Defined Benefit Plan, Expected Future Benefit Payment, Year Three		3,519
Defined Benefit Plan, Expected Future Benefit Payment, Year Four		3,454
Defined Benefit Plan, Expected Future Benefit Payment, Year Five		3,446
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter		16,385
Other Postretirement Benefits Plan [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,043	$ 1,793
Other Postretirement Benefits Plan [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		37,017	29,007
Other Postretirement Benefits Plan [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		39,060	30,800
Other Postretirement Benefits Plan [Member] | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,043	1,792
Other Postretirement Benefits Plan [Member] | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Equity securities | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,043	1,792
Other Postretirement Benefits Plan [Member] | Money market funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	1
Other Postretirement Benefits Plan [Member] | Money market funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,428	413
Other Postretirement Benefits Plan [Member] | Money market funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Money market funds | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,428	414
Other Postretirement Benefits Plan [Member] | Insurance and group annuity contracts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Insurance and group annuity contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		34,589	28,594
Other Postretirement Benefits Plan [Member] | Insurance and group annuity contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Other Postretirement Benefits Plan [Member] | Insurance and group annuity contracts | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		34,589	28,594
Supplemental Executive Retirement Plan Investments Included in Other Assets[Member]
Defined Benefit Plan Disclosure [Line Items]
Balance at December 31		$ 98,900	87,700
401(k) Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Percent of employee matched of eligible compensation		100.00%
Percentage of Each Participants Eligible Compensation		1.00%
Contributions made to the Plan		$ 30,400	$ 28,000	$ 21,100
Profit-sharing contribution [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of Each Participants Eligible Compensation		6.00%

INCOME TAXES (Details)

INCOME TAXES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current tax expense (benefit)
Federal	$ (1,278)	$ 260	$ 295
State	963	1,633	1,670
Total current tax expense (benefit)	(315)	1,893	1,965
Deferred tax expense
Federal	327,806	319,551	376,728
State	44,923	41,459	68,589
Total deferred tax expense	372,729	361,010	445,317
Income taxes	372,414	362,903	447,282
Income Tax Reconciliation
Income before income taxes	1,650,991	1,517,935	1,040,801
Less: Net income attributable to noncontrolling interests	0	3,329	205,678
Net income attributable to ONEOK before income taxes	$ 1,650,991	$ 1,514,606	$ 835,123
Federal statutory income tax rate	21.00%	21.00%	35.00%
Provision for federal income taxes	$ 346,708	$ 318,067	$ 292,293
State income taxes, net of federal benefit	34,545	38,668	16,197
Deferred tax rate change, inclusive of valuation allowance	11,340	5,552	141,283
Other, net	804	5,260	(2,491)
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(20,983)	(4,644)	0
Deferred tax assets
Employee benefits and other accrued liabilities	99,510	91,587
Federal net operating loss	858,030	420,318
State net operating loss and benefits	171,779	108,004
Derivative instruments	83,710	22,108
Other	12,769	13,378
Total deferred tax assets	1,225,798	655,395
Carryforward expected to expire prior to utilization	(94,794)	(73,820)
Net deferred tax assets	1,131,004	581,575
Deferred tax liabilities
Excess of tax over book depreciation	84,631	73,113
Investment in partnerships (a)	1,582,436	728,193
Total deferred tax liabilities	1,667,067	801,306
Net deferred tax assets (liabilities)	536,063	219,731
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 11,300	$ 5,600	$ 54,100

UNCONSOLIDATED AFFILIATES (Deta

UNCONSOLIDATED AFFILIATES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%
Investments in unconsolidated affiliates	$ 861,844	$ 969,150	$ 1,003,156
Equity method goodwill	38,800	38,800
Equity in net earnings from investments	154,541	158,383	159,278
Impairment of equity investments	0	0	(4,270)
Balance Sheet [Abstract]
Current assets	149,564	158,723
Property, plant and equipment, net	2,314,631	2,413,662
Other noncurrent assets	13,252	16,273
Current liabilities	88,142	83,057
Long-term debt	581,327	480,731
Other noncurrent liabilities	76,685	47,826
Accumulated other comprehensive income (loss)	(28,373)	2,053
Owners’ equity	1,759,666	1,974,991
Income Statement [Abstract]
Revenues	634,135	637,762	639,102
Operating expenses	291,210	276,373	277,121
Net income	315,274	337,694	347,692
Distributions paid to us	257,644	197,285	196,114
Accounts Payable, Related Parties, Current	13,500	14,700
Unconsolidated Affiliates [Member]
Income Statement [Abstract]
Related Party Transaction, Expenses from Transactions with Related Party	$ 164,700	$ 153,900	156,100
Northern Border Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%	50.00%
Investments in unconsolidated affiliates	$ 307,209	$ 381,623
Equity in net earnings from investments	68,871	67,854	68,153
Income Statement [Abstract]
Distributions paid to us	50,000
Payments to Acquire Equity Method Investments	$ 0	$ 0	83,000
Overland Pass Pipeline Company [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%	50.00%
Investments in unconsolidated affiliates	$ 417,473	$ 429,295
Equity in net earnings from investments	$ 63,698	$ 65,887	60,067
Roadrunner Gas Transmission [Member]
Schedule of Equity Method Investments [Line Items]
Net ownership percentage	50.00%	50.00%
Investments in unconsolidated affiliates	$ 80,816	$ 93,857
Equity in net earnings from investments	26,839	22,993	19,150
Other Unconsolidated Affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates	56,346	64,375
Equity in net earnings from investments	$ (4,867)	$ 1,649	$ 11,908

COMMITMENTS AND CONTINGENCIES_3

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Dec. 31, 2019USD ($)
Firm Transportation and Storage Contracts [Abstract]
2019	$ 61.6
2020	48.1
2021	40.1
2022	36.4
2023	34.3
Thereafter	177.9
Total	$ 398.4

LEASES (Details)

LEASES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Details [Line Items]
Lease, Operating Lease, Lease not Yet Commenced, Liability	$ 75,600
Operating cash flows for operating leases	6,213
Financing cash flows for finance lease	1,764
Right-of-Use Assets Obtained in Exchange for Operating Lease Liability	$ 4,097
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	10 years
Finance lease assets- Accumulated depreciation	$ (3,702,807)		$ (3,264,312)
Finance lease liability - current	1,949		1,765
Finance lease, liability - noncurrent	24,296		$ 26,244
Lease Assets and Liabilities Included in the Consolidated Balance Sheet [Member]
Lessee, Lease, Details [Line Items]
Operating lease assets - Other assets	15,147
Operating lease, liabilities - Other current liabilities	1,883
Finance lease assets - PPE	28,286
Finance lease assets- Accumulated depreciation	(1,320)
Total leased assets	42,113
Finance lease liability - current	1,949
Operating lease, liabilities - Other deferred credits	13,509
Finance lease, liability - noncurrent	24,296
Total lease liabilities	41,637
Components of Lease Cost [Member]
Lessee, Lease, Details [Line Items]
Operating leases - Operations and maintenance	6,803
Finance lease - Amortization of lease assets	1,131
Finance Lease - Interest on lease liabilities	2,721
Total lease cost	$ 10,655
Weighted-Average Remaining Lease Term [Member]
Lessee, Lease, Details [Line Items]
Operating Lease, Weighted Average Remaining Lease Term	10 years 4 months 24 days
Finance Lease, Weighted Average Remaining Lease Term	8 years 9 months 18 days
Weighted-Average Discount Rate [Member]
Lessee, Lease, Details [Line Items]
Operating Lease, Weighted Average Discount Rate, Percent	4.58%
Finance Lease, Weighted Average Discount Rate, Percent	10.00%
Maturity of Finance Lease Liability [Member]
Lessee, Lease, Details [Line Items]
2020	$ 4,500
2021	4,500
2022	4,500
2023	4,500
2024	4,500
2025 and beyond	17,100
Total lease payments	39,600
Less: Interest	13,400
Present value of lease liabilities	26,200
Maturity of Operating Lease Liabilities [Member]
Lessee, Lease, Details [Line Items]
2020	2,500
2021	2,100
2022	2,000
2023	1,900
2024	1,900
2025 and beyond	9,200
Total lease payments	19,600
Less: Interest	4,200
Present value of lease liabilities	$ 15,400
Accounting Standards Update 2016-02 [Member]
Lessee, Lease, Details [Line Items]
Operating lease assets - Other assets		$ 17,500
Present value of lease liabilities		28,000
Present value of lease liabilities		17,400
Finance lease assets - PPE		$ 28,100

REVENUES (Details)

REVENUES (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Contract with Customer, Asset and Liability [Abstract]
Contract with customer, assets	$ 5	$ 6.2	$ 6.4
Amounts invoiced in excess of revenue recognized	(1.7)	(0.9)
Net additions, assets	0.5	0.7
Contract with customer, asset, net, current	1.3	1.7	0.9
Contract with customer, asset, net, noncurrent	3.7	4.5
Contract with customer, liabilities	57.1	31.7	33.3
Revenue recognized included in beginning balance	(15.6)	(19.5)
Net additions, liabilities	41	17.9
Contract with customer, liability, current	22.2	15.6	$ 19.5
Contract with customer, liability, noncurrent	34.9	$ 16.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1,822.3
Revenue, Remaining Performance Obligation, Contract Term	5 to 10 years
2020 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 343.5
2021 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	290.4
2022 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	214.8
2023 [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	166.4
Thereafter [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 807.2
Remaining Contract Terms [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Contract Term	one month to 24 years

SEGMENTS (Details)

SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Segment Reporting, Disclosure of Major Customers										For the year ended December 31, 2019, we had no single customer from which we received 10% or more of our consolidated revenues.	For the year ended December 31, 2018, we had no single customer from which we received 10% or more of our consolidated revenues.	For the year ended December 31, 2017, we had no single customer from which we received 10% or more of our consolidated revenues.
Total revenues	$ 2,663,606	$ 2,263,228	$ 2,457,575	$ 2,779,958	$ 3,136,700	$ 3,393,890	$ 2,960,529	$ 3,102,077		$ 10,164,367	$ 12,593,196	$ 12,173,907
Cost of sales and fuel (exclusive of depreciation and operating costs)										(6,788,040)	(9,422,708)	(9,538,045)
Operating costs										(982,864)	(907,068)	(822,710)
Equity in net earnings from investments										154,541	158,383	159,278
Depreciation and amortization										(476,535)	(428,557)	(406,335)
Asset Impairment Charges										0	0	(20,240)
Investments in unconsolidated affiliates	861,844				969,150					861,844	969,150	1,003,156
Noncash compensation expense										26,699	37,954	13,421
Total assets	21,812,121				18,231,671					21,812,121	18,231,671	16,845,937
Capital expenditures										3,848,349	2,141,475	512,393
Operating income	487,314	482,151	476,146	468,742	471,865	495,534	448,366	419,699		1,914,353	1,835,464	1,391,771
Net income	320,251	$ 309,155	$ 311,963	$ 337,208	292,888	$ 313,916	$ 282,179	$ 266,049		1,278,577	1,155,032	593,519
Interest expense, net of capitalized interest										491,773	469,620	485,658
Income taxes										372,414	362,903	447,282
Other corporate costs and noncash items										(68,767)	(15,603)	46,774
Noncash Contribution Expense										0	0	12,600
Business Combination, Acquisition Related Costs												30,000
Series E Preferred Stock [Member]
Segment Reporting Information [Line Items]
Noncash Contribution Expense									$ 20,000			20,000
Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Total revenues										2,368,639	3,034,577	3,026,574
Cost of sales and fuel (exclusive of depreciation and operating costs)										(1,302,310)	(2,041,448)	(2,216,355)
Operating costs										(368,352)	(368,939)	(307,376)
Equity in net earnings from investments										(6,292)	410	12,098
Noncash compensation expense and other										10,965	7,007	3,531
Segment adjusted EBITDA										702,650	631,607	518,472
Depreciation and amortization										(219,519)	(196,090)	(184,923)
Asset Impairment Charges												(20,240)
Investments in unconsolidated affiliates	34,426				42,630					34,426	42,630	55,841
Total assets	6,795,744				6,078,473					6,795,744	6,078,473	5,495,163
Capital expenditures										926,489	694,611	284,205
Natural Gas Gathering And Processing | Natural Gas Gathering and Processing Intersegment [Member]
Segment Reporting Information [Line Items]
Total revenues										1,200,000	1,800,000
Natural Gas Liquids
Segment Reporting Information [Line Items]
Total revenues										8,532,516	10,934,578	10,626,204
Cost of sales and fuel (exclusive of depreciation and operating costs)										(6,690,918)	(9,176,813)	(9,176,494)
Operating costs										(456,892)	(394,115)	(358,278)
Equity in net earnings from investments										65,123	67,126	59,876
Noncash compensation expense and other										15,936	9,829	3,631
Segment adjusted EBITDA										1,465,765	1,440,605	1,154,939
Depreciation and amortization										(196,132)	(174,007)	(167,277)
Asset Impairment Charges												0
Investments in unconsolidated affiliates	439,393				451,040					439,393	451,040	457,467
Total assets	12,551,476				9,663,640					12,551,476	9,663,640	8,782,700
Capital expenditures										2,796,604	1,306,341	114,267
Natural Gas Liquids | Natural Gas Liquids Regulated [Member]
Segment Reporting Information [Line Items]
Total revenues										1,400,000	1,200,000	1,200,000
Cost of sales and fuel (exclusive of depreciation and operating costs)										(496,800)	(506,000)	(497,400)
Natural Gas Pipelines
Segment Reporting Information [Line Items]
Total revenues										471,987	431,735	419,932
Cost of sales and fuel (exclusive of depreciation and operating costs)										(4,628)	(15,984)	(43,424)
Operating costs										(157,230)	(144,259)	(125,308)
Equity in net earnings from investments										95,710	90,847	87,304
Noncash compensation expense and other										2,977	3,912	1,314
Segment adjusted EBITDA										408,816	366,251	339,818
Depreciation and amortization										(57,250)	(55,118)	(51,025)
Asset Impairment Charges												0
Investments in unconsolidated affiliates	388,025				475,480					388,025	475,480	489,848
Total assets	2,094,072				2,131,669					2,094,072	2,131,669	2,055,020
Capital expenditures										99,221	119,185	95,564
Natural Gas Pipelines | Natural Gas Pipelines Regulated [Member]
Segment Reporting Information [Line Items]
Total revenues										285,300	266,600	264,900
Cost of sales and fuel (exclusive of depreciation and operating costs)										(20,000)	(26,000)	(44,000)
Total Segments [Member]
Segment Reporting Information [Line Items]
Total revenues										11,373,142	14,400,890	14,072,710
Cost of sales and fuel (exclusive of depreciation and operating costs)										(7,997,856)	(11,234,245)	(11,436,273)
Operating costs										(982,474)	(907,313)	(790,962)
Equity in net earnings from investments										154,541	158,383	159,278
Noncash compensation expense and other										29,878	20,748	8,476
Segment adjusted EBITDA										2,577,231	2,438,463	2,013,229
Depreciation and amortization										(472,901)	(425,215)	(403,225)
Asset Impairment Charges												(20,240)
Investments in unconsolidated affiliates	861,844				969,150					861,844	969,150	1,003,156
Total assets	21,441,292				17,873,782					21,441,292	17,873,782	16,332,883
Capital expenditures										3,822,314	2,120,137	494,036
Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										(1,208,775)	(1,807,694)	(1,898,803)
Cost of sales and fuel (exclusive of depreciation and operating costs)										1,209,816	1,811,537	1,898,228
Operating costs										(390)	245	(31,748)
Equity in net earnings from investments										0	0	0
Depreciation and amortization										(3,634)	(3,342)	(3,110)
Asset Impairment Charges												0
Investments in unconsolidated affiliates	0				0					0	0	0
Total assets	$ 370,829				$ 357,889					370,829	357,889	513,054
Capital expenditures										26,035	21,338	18,357
Unaffiliated entity [Member]
Segment Reporting Information [Line Items]
Total revenues												12,173,907
Unaffiliated entity [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Total revenues												1,750,655
Unaffiliated entity [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Total revenues												10,009,576
Unaffiliated entity [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Total revenues												411,490
Unaffiliated entity [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Total revenues												12,171,721
Unaffiliated entity [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues												2,186
Intersegment [Member]
Segment Reporting Information [Line Items]
Total revenues												0
Intersegment [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Total revenues												1,275,919
Intersegment [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Total revenues												616,628
Intersegment [Member] | Natural Gas Liquids | Natural Gas Liquids Regulated [Member]
Segment Reporting Information [Line Items]
Total revenues										1,200,000	1,100,000	1,000,000
Intersegment [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Total revenues												8,442
Intersegment [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Total revenues												1,900,989
Intersegment [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues												$ (1,900,989)
Noncustomer [Domain]
Segment Reporting Information [Line Items]
Total revenues										139,600	(16,200)
NGL and Condensate Sales [Member]
Segment Reporting Information [Line Items]
Total revenues										7,944,787	10,301,496
NGL and Condensate Sales [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										1,224,378	1,775,991
NGL and Condensate Sales [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										7,910,833	10,319,847
NGL and Condensate Sales [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
NGL and Condensate Sales [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										9,135,211	12,095,838
NGL and Condensate Sales [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										(1,190,424)	(1,794,342)
Residue Natural Gas Sales [Member]
Segment Reporting Information [Line Items]
Total revenues										965,975	1,091,102
Residue Natural Gas Sales [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										966,149	1,084,162
Residue Natural Gas Sales [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Residue Natural Gas Sales [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										1,244	9,772
Residue Natural Gas Sales [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										967,393	1,093,934
Residue Natural Gas Sales [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										(1,418)	(2,832)
Gathering and Exchange Services Revenue [Member]
Segment Reporting Information [Line Items]
Total revenues										578,537	568,070
Gathering and Exchange Services Revenue [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										164,299	163,194
Gathering and Exchange Services Revenue [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										414,238	404,897
Gathering and Exchange Services Revenue [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Gathering and Exchange Services Revenue [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										578,537	568,091
Gathering and Exchange Services Revenue [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										0	(21)
Transportation and Storage Revenue [Member]
Segment Reporting Information [Line Items]
Total revenues										648,103	603,437
Transportation and Storage Revenue [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										0	0
Transportation and Storage Revenue [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										197,483	199,018
Transportation and Storage Revenue [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										466,266	414,969
Transportation and Storage Revenue [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax										663,749	613,987
Transportation and Storage Revenue [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										(15,646)	(10,550)
Other [Member]
Segment Reporting Information [Line Items]
Total revenues										26,965	29,091
Other [Member] | Natural Gas Gathering And Processing
Segment Reporting Information [Line Items]
Total revenues										13,813	11,230
Other [Member] | Natural Gas Liquids
Segment Reporting Information [Line Items]
Total revenues										9,962	10,816
Other [Member] | Natural Gas Pipelines
Segment Reporting Information [Line Items]
Total revenues										4,477	6,994
Other [Member] | Total Segments [Member]
Segment Reporting Information [Line Items]
Total revenues										28,252	29,040
Other [Member] | Other and Eliminations
Segment Reporting Information [Line Items]
Total revenues										$ (1,287)	$ 51

QUARTERLY FINANCIAL DATA (UNA_3

QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total revenues	$ 2,663,606	$ 2,263,228	$ 2,457,575	$ 2,779,958	$ 3,136,700	$ 3,393,890	$ 2,960,529	$ 3,102,077	$ 10,164,367	$ 12,593,196	$ 12,173,907
Operating income	487,314	482,151	476,146	468,742	471,865	495,534	448,366	419,699	1,914,353	1,835,464	1,391,771
Net income	320,251	309,155	311,963	337,208	292,888	313,916	282,179	266,049	1,278,577	1,155,032	593,519
Net income available to common shareholders	$ 319,976	$ 308,880	$ 311,688	$ 336,933	$ 292,613	$ 312,984	$ 280,773	$ 264,233	$ 1,277,477	$ 1,150,603	$ 387,074
Earnings per share- Basic	$ 0.77	$ 0.75	$ 0.75	$ 0.82	$ 0.71	$ 0.76	$ 0.68	$ 0.65	$ 3.09	$ 2.80	$ 1.30
Earnings per share- Diluted	$ 0.77	$ 0.74	$ 0.75	$ 0.81	$ 0.70	$ 0.75	$ 0.68	$ 0.64	$ 3.07	$ 2.78	$ 1.29

SUPPLEMENTAL CONDENSED CONSOL_3

SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION CONDENSED CONSOLIDATING FINANCIAL STATEMENTS, Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Equity Method Investment, Ownership Percentage	50.00%								50.00%
Revenues	$ 2,663,606	$ 2,263,228	$ 2,457,575	$ 2,779,958	$ 3,136,700	$ 3,393,890	$ 2,960,529	$ 3,102,077	$ 10,164,367	$ 12,593,196	$ 12,173,907
Cost of sales and fuel (exclusive of items shown separately below)									6,788,040	9,422,708	9,538,045
Impairment of long-lived assets									0	0	15,970
(Gain) loss on sale of assets									2,575	(601)	(924)
Operating income	487,314	482,151	476,146	468,742	471,865	495,534	448,366	419,699	1,914,353	1,835,464	1,391,771
Equity in net earnings from investments									154,541	158,383	159,278
Impairment of equity investments									0	0	(4,270)
Interest expense, net									(491,773)	(469,620)	(485,658)
Income before income taxes									1,650,991	1,517,935	1,040,801
Income taxes									(372,414)	(362,903)	(447,282)
Net income	320,251	309,155	311,963	337,208	292,888	313,916	282,179	266,049	1,278,577	1,155,032	593,519
Less: Net income attributable to noncontrolling interests									0	3,329	205,678
Net income attributable to ONEOK									1,278,577	1,151,703	387,841
Less: Preferred stock dividends									1,100	1,100	767
Net income available to common shareholders	$ 319,976	$ 308,880	$ 311,688	$ 336,933	$ 292,613	$ 312,984	$ 280,773	$ 264,233	1,277,477	1,150,603	387,074
Other Comprehensive Income (Loss), Net of Tax									(185,761)	38,392	37,134
Comprehensive income									1,092,816	1,193,424	630,653
Less: Comprehensive income attributable to noncontrolling interests									0	3,329	236,704
Comprehensive income attributable to ONEOK									$ 1,092,816	$ 1,190,095	393,949
Northern Border Pipeline [Member]
Condensed Financial Statements, Captions [Line Items]
Equity Method Investment, Ownership Percentage	50.00%				50.00%				50.00%	50.00%
Equity in net earnings from investments									$ 68,871	$ 67,854	68,153
Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									8,916,047	11,395,642	9,862,652
Services
Condensed Financial Statements, Captions [Line Items]
Revenues									1,248,320	1,197,554	2,311,255
Reportable Legal Entities | Parent Issuer & Guarantor
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Cost of sales and fuel (exclusive of items shown separately below)									0	0	0
Operating expenses									0	(600)	17,800
Impairment of long-lived assets											0
(Gain) loss on sale of assets									0	0	0
Operating income									0	600	(17,800)
Equity in net earnings from investments									1,898,700	1,655,600	1,236,600
Impairment of equity investments											0
Other income (expense), net									34,400	29,600	(12,300)
Interest expense, net									(287,400)	(179,400)	(137,100)
Income before income taxes									1,645,700	1,506,400	1,069,400
Income taxes									(367,100)	(354,700)	(480,200)
Net income									1,278,600	1,151,700	589,200
Less: Net income attributable to noncontrolling interests										0	201,400
Net income attributable to ONEOK									1,278,600	1,151,700	387,800
Less: Preferred stock dividends									1,100	1,100	800
Net income available to common shareholders									1,277,500	1,150,600	387,000
Other Comprehensive Income (Loss), Net of Tax									(183,800)	(39,500)	17,400
Comprehensive income									1,094,800	1,112,200	606,600
Less: Comprehensive income attributable to noncontrolling interests										0	232,400
Comprehensive income attributable to ONEOK										1,112,200	374,200
Reportable Legal Entities | Parent Issuer & Guarantor | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Parent Issuer & Guarantor | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Subsidiary Issuer & Guarantor
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Cost of sales and fuel (exclusive of items shown separately below)									0	0	0
Operating expenses									0	0	0
Impairment of long-lived assets											0
(Gain) loss on sale of assets									0	0	0
Operating income									0	0	0
Equity in net earnings from investments									1,906,200	1,660,500	1,215,700
Impairment of equity investments											0
Other income (expense), net									305,700	315,100	353,100
Interest expense, net									(308,300)	(315,100)	(353,100)
Income before income taxes									1,903,600	1,660,500	1,215,700
Income taxes									0	0	0
Net income									1,903,600	1,660,500	1,215,700
Less: Net income attributable to noncontrolling interests										0	0
Net income attributable to ONEOK									1,903,600	1,660,500	1,215,700
Less: Preferred stock dividends									0	0	0
Net income available to common shareholders									1,903,600	1,660,500	1,215,700
Other Comprehensive Income (Loss), Net of Tax									(2,600)	101,100	13,200
Comprehensive income									1,901,000	1,761,600	1,228,900
Less: Comprehensive income attributable to noncontrolling interests										0	0
Comprehensive income attributable to ONEOK										1,761,600	1,228,900
Reportable Legal Entities | Subsidiary Issuer & Guarantor | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Subsidiary Issuer & Guarantor | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Guarantor Subsidiary
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Cost of sales and fuel (exclusive of items shown separately below)									0	0	0
Operating expenses									0	0	9,200
Impairment of long-lived assets											0
(Gain) loss on sale of assets									2,700	0	0
Operating income									(2,700)	0	(9,200)
Equity in net earnings from investments									1,908,900	1,660,500	1,224,900
Impairment of equity investments											0
Other income (expense), net									308,300	315,100	353,100
Interest expense, net									(308,300)	(315,100)	(353,100)
Income before income taxes									1,906,200	1,660,500	1,215,700
Income taxes									0	0	0
Net income									1,906,200	1,660,500	1,215,700
Less: Net income attributable to noncontrolling interests										0	0
Net income attributable to ONEOK									1,906,200	1,660,500	1,215,700
Less: Preferred stock dividends									0	0	0
Net income available to common shareholders									1,906,200	1,660,500	1,215,700
Other Comprehensive Income (Loss), Net of Tax									(20,900)	85,900	27,900
Comprehensive income									1,885,300	1,746,400	1,243,600
Less: Comprehensive income attributable to noncontrolling interests										0	0
Comprehensive income attributable to ONEOK										1,746,400	1,243,600
Reportable Legal Entities | Guarantor Subsidiary | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Guarantor Subsidiary | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Reportable Legal Entities | Combined Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues									10,166,500	12,595,300	12,175,900
Cost of sales and fuel (exclusive of items shown separately below)									6,788,000	9,422,700	9,538,000
Operating expenses									1,461,500	1,338,300	1,204,000
Impairment of long-lived assets											16,000
(Gain) loss on sale of assets									(100)	(600)	(900)
Operating income									1,917,100	1,834,900	1,418,800
Equity in net earnings from investments									116,300	116,300	100,700
Impairment of equity investments											(4,300)
Other income (expense), net									42,100	(36,000)	(8,000)
Interest expense, net									(204,400)	(290,200)	(348,600)
Income before income taxes									1,871,100	1,625,000	1,158,600
Income taxes									(5,300)	(8,200)	32,900
Net income									1,865,800	1,616,800	1,191,500
Less: Net income attributable to noncontrolling interests										3,300	4,300
Net income attributable to ONEOK									1,865,800	1,613,500	1,187,200
Less: Preferred stock dividends									0	0	0
Net income available to common shareholders									1,865,800	1,613,500	1,187,200
Other Comprehensive Income (Loss), Net of Tax									(20,500)	62,600	34,500
Comprehensive income									1,845,300	1,679,400	1,226,000
Less: Comprehensive income attributable to noncontrolling interests										3,300	4,300
Comprehensive income attributable to ONEOK										1,676,100	1,221,700
Reportable Legal Entities | Combined Non-Guarantor Subsidiaries | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									8,916,100	11,395,600	9,862,700
Reportable Legal Entities | Combined Non-Guarantor Subsidiaries | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									1,250,400	1,199,700	2,313,200
Reportable Legal Entities | Total
Condensed Financial Statements, Captions [Line Items]
Revenues									10,164,400	12,593,200	12,173,900
Cost of sales and fuel (exclusive of items shown separately below)									6,788,000	9,422,700	9,538,000
Operating expenses									1,459,400	1,335,600	1,229,000
Impairment of long-lived assets											16,000
(Gain) loss on sale of assets									2,600	(600)	(900)
Operating income									1,914,400	1,835,500	1,391,800
Equity in net earnings from investments									154,500	158,400	159,300
Impairment of equity investments											(4,300)
Other income (expense), net									73,900	(6,400)	(20,300)
Interest expense, net									(491,800)	(469,600)	(485,700)
Income before income taxes									1,651,000	1,517,900	1,040,800
Income taxes									(372,400)	(362,900)	(447,300)
Net income									1,278,600	1,155,000	593,500
Less: Net income attributable to noncontrolling interests										3,300	205,700
Net income attributable to ONEOK									1,278,600	1,151,700	387,800
Less: Preferred stock dividends									1,100	1,100	800
Net income available to common shareholders									1,277,500	1,150,600	387,000
Other Comprehensive Income (Loss), Net of Tax									(185,800)	38,400	37,100
Comprehensive income									1,092,800	1,193,400	630,600
Less: Comprehensive income attributable to noncontrolling interests										3,300	236,700
Comprehensive income attributable to ONEOK										1,190,100	393,900
Reportable Legal Entities | Total | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									8,916,100	11,395,600	9,862,700
Reportable Legal Entities | Total | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									1,248,300	1,197,600	2,311,200
Consolidating Entries and Other
Condensed Financial Statements, Captions [Line Items]
Revenues									(2,100)	(2,100)	(2,000)
Cost of sales and fuel (exclusive of items shown separately below)									0	0	0
Operating expenses									(2,100)	(2,100)	(2,000)
Impairment of long-lived assets											0
(Gain) loss on sale of assets									0	0	0
Operating income									0	0	0
Equity in net earnings from investments									(5,675,600)	(4,934,500)	(3,618,600)
Impairment of equity investments											0
Other income (expense), net									(616,600)	(630,200)	(706,200)
Interest expense, net									616,600	630,200	706,200
Income before income taxes									(5,675,600)	(4,934,500)	(3,618,600)
Income taxes									0	0	0
Net income									(5,675,600)	(4,934,500)	(3,618,600)
Less: Net income attributable to noncontrolling interests										0	0
Net income attributable to ONEOK									(5,675,600)	(4,934,500)	(3,618,600)
Less: Preferred stock dividends									0	0	0
Net income available to common shareholders									(5,675,600)	(4,934,500)	(3,618,600)
Other Comprehensive Income (Loss), Net of Tax									42,000	(171,700)	(55,900)
Comprehensive income									(5,633,600)	(5,106,200)	(3,674,500)
Less: Comprehensive income attributable to noncontrolling interests										0	0
Comprehensive income attributable to ONEOK										(5,106,200)	(3,674,500)
Consolidating Entries and Other | Commodity Sales
Condensed Financial Statements, Captions [Line Items]
Revenues									0	0	0
Consolidating Entries and Other | Services
Condensed Financial Statements, Captions [Line Items]
Revenues									$ (2,100)	$ (2,100)	$ (2,000)

SUPPLEMENTAL CONDENSED CONSOL_4

SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION CONDENSED CONSOLIDATING FINANCIAL STATEMENTS, Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 20,958	$ 11,975	$ 37,193	$ 248,875
Accounts receivable, net	835,121	818,958
Materials and supplies	201,749	141,174
Natural gas and NGLs in storage	304,926	296,667
Other current assets	82,313	100,808
Total current assets	1,470,334	1,398,632
Property, plant and equipment
Property, plant and equipment	22,051,492	18,030,963
Accumulated depreciation and amortization	3,702,807	3,264,312
Net property, plant and equipment	18,348,685	14,766,651
Investments and other assets
Investments	861,844	969,150	1,003,156
Other assets	173,425	130,096
Total investments and other assets	1,993,102	2,066,388
Total assets	21,812,121	18,231,671	16,845,937
Current liabilities
Current maturities of long-term debt	7,650	507,650
Short-term borrowings	220,000	0
Accounts payable	1,209,900	1,116,337
Other current liabilities	285,569	211,110
Total current liabilities	2,020,298	2,108,436
Long-term debt, excluding current maturities	12,479,757	8,873,334
Deferred income taxes	536,063	219,731
Other deferred credits	525,756	424,383
Deferred credits and other liabilities	1,086,115	670,358
Commitments and contingencies
Equity
Equity excluding noncontrolling interests in consolidated subsidiaries	6,225,951	6,579,543
Total equity	6,225,951	6,579,543	5,685,352	3,428,915
Total liabilities and equity	21,812,121	18,231,671
Reportable Legal Entities | Parent Issuer & Guarantor
Current assets
Cash and cash equivalents	21,000	12,000	37,200	248,500
Accounts receivable, net	0	0
Materials and supplies	0	0
Natural gas and NGLs in storage	0	0
Other current assets	12,400	29,100
Total current assets	33,400	41,100
Property, plant and equipment
Property, plant and equipment	166,600	145,500
Accumulated depreciation and amortization	99,500	92,000
Net property, plant and equipment	67,100	53,500
Investments and other assets
Investments	6,732,600	6,153,500
Intercompany notes receivable	8,950,900	5,308,600
Other assets	139,900	115,900
Total investments and other assets	15,823,400	11,578,000
Total assets	15,923,900	11,672,600
Current liabilities
Current maturities of long-term debt	0	0
Short-term borrowings	220,000
Accounts payable	23,800	31,300
Other current liabilities	243,800	123,200
Total current liabilities	487,600	154,500
Intercompany payables	0	0
Long-term debt, excluding current maturities	8,421,100	4,510,700
Deferred income taxes	417,100	112,300
Other deferred credits	372,100	315,600
Deferred credits and other liabilities	789,200	427,900
Commitments and contingencies
Equity
Total equity	6,226,000	6,579,500
Total liabilities and equity	15,923,900	11,672,600
Reportable Legal Entities | Subsidiary Issuer & Guarantor
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	0	0
Materials and supplies	0	0
Natural gas and NGLs in storage	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant and equipment
Property, plant and equipment	0	0
Accumulated depreciation and amortization	0	0
Net property, plant and equipment	0	0
Investments and other assets
Investments	4,101,400	3,548,100
Intercompany notes receivable	6,903,200	7,701,500
Other assets	0	0
Total investments and other assets	11,004,600	11,249,600
Total assets	11,004,600	11,249,600
Current liabilities
Current maturities of long-term debt	0	500,000
Short-term borrowings	0
Accounts payable	0	0
Other current liabilities	63,300	81,000
Total current liabilities	63,300	581,000
Intercompany payables	0	0
Long-term debt, excluding current maturities	4,045,100	4,341,400
Deferred income taxes	0	0
Other deferred credits	0	0
Deferred credits and other liabilities	0	0
Commitments and contingencies
Equity
Total equity	6,896,200	6,327,200
Total liabilities and equity	11,004,600	11,249,600
Reportable Legal Entities | Guarantor Subsidiary
Current assets
Cash and cash equivalents	0	0	0	400
Accounts receivable, net	0	0
Materials and supplies	0	0
Natural gas and NGLs in storage	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant and equipment
Property, plant and equipment	0	0
Accumulated depreciation and amortization	0	0
Net property, plant and equipment	0	0
Investments and other assets
Investments	11,466,300	9,721,600
Intercompany notes receivable	0	1,528,000
Other assets	0	0
Total investments and other assets	11,466,300	11,249,600
Total assets	11,466,300	11,249,600
Current liabilities
Current maturities of long-term debt	0	0
Short-term borrowings	0
Accounts payable	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Intercompany payables	7,364,900	7,701,500
Long-term debt, excluding current maturities	0	0
Deferred income taxes	0	0
Other deferred credits	0	0
Deferred credits and other liabilities	0	0
Commitments and contingencies
Equity
Total equity	4,101,400	3,548,100
Total liabilities and equity	11,466,300	11,249,600
Reportable Legal Entities | Combined Non-Guarantor Subsidiaries
Current assets
Cash and cash equivalents	0	0	0	0
Accounts receivable, net	835,100	819,000
Materials and supplies	201,700	141,200
Natural gas and NGLs in storage	304,900	296,700
Other current assets	95,200	100,600
Total current assets	1,436,900	1,357,500
Property, plant and equipment
Property, plant and equipment	21,884,900	17,885,500
Accumulated depreciation and amortization	3,603,300	3,172,300
Net property, plant and equipment	18,281,600	14,713,200
Investments and other assets
Investments	769,900	791,100
Intercompany notes receivable	0	0
Other assets	992,100	982,300
Total investments and other assets	1,762,000	1,773,400
Total assets	21,480,500	17,844,100
Current liabilities
Current maturities of long-term debt	7,700	7,700
Short-term borrowings	0
Accounts payable	1,186,100	1,085,000
Other current liabilities	275,600	280,200
Total current liabilities	1,469,400	1,372,900
Intercompany payables	8,489,200	6,836,600
Long-term debt, excluding current maturities	13,500	21,200
Deferred income taxes	119,700	108,400
Other deferred credits	177,900	135,200
Deferred credits and other liabilities	297,600	243,600
Commitments and contingencies
Equity
Total equity	11,210,800	9,369,800
Total liabilities and equity	21,480,500	17,844,100
Reportable Legal Entities | Total
Current assets
Cash and cash equivalents	21,000	12,000	37,200	248,900
Accounts receivable, net	835,100	819,000
Materials and supplies	201,700	141,200
Natural gas and NGLs in storage	304,900	296,700
Other current assets	107,600	129,700
Total current assets	1,470,300	1,398,600
Property, plant and equipment
Property, plant and equipment	22,051,500	18,031,000
Accumulated depreciation and amortization	3,702,800	3,264,300
Net property, plant and equipment	18,348,700	14,766,700
Investments and other assets
Investments	861,800	969,200
Intercompany notes receivable	0	0
Other assets	1,131,300	1,097,200
Total investments and other assets	1,993,100	2,066,400
Total assets	21,812,100	18,231,700
Current liabilities
Current maturities of long-term debt	7,700	507,700
Short-term borrowings	220,000
Accounts payable	1,209,900	1,116,300
Other current liabilities	582,700	484,400
Total current liabilities	2,020,300	2,108,400
Intercompany payables	0	0
Long-term debt, excluding current maturities	12,479,700	8,873,300
Deferred income taxes	536,100	219,700
Other deferred credits	550,000	450,800
Deferred credits and other liabilities	1,086,100	670,500
Commitments and contingencies
Equity
Total equity	6,226,000	6,579,500
Total liabilities and equity	21,812,100	18,231,700
Consolidating Entries and Other
Current assets
Cash and cash equivalents	0	0	$ 0	$ 0
Accounts receivable, net	0	0
Materials and supplies	0	0
Natural gas and NGLs in storage	0	0
Other current assets	0	0
Total current assets	0	0
Property, plant and equipment
Property, plant and equipment	0	0
Accumulated depreciation and amortization	0	0
Net property, plant and equipment	0	0
Investments and other assets
Investments	(22,208,400)	(19,245,100)
Intercompany notes receivable	(15,854,100)	(14,538,100)
Other assets	(700)	(1,000)
Total investments and other assets	(38,063,200)	(33,784,200)
Total assets	(38,063,200)	(33,784,200)
Current liabilities
Current maturities of long-term debt	0	0
Short-term borrowings	0
Accounts payable	0	0
Other current liabilities	0	0
Total current liabilities	0	0
Intercompany payables	(15,854,100)	(14,538,100)
Long-term debt, excluding current maturities	0	0
Deferred income taxes	(700)	(1,000)
Other deferred credits	0	0
Deferred credits and other liabilities	(700)	(1,000)
Commitments and contingencies
Equity
Total equity	(22,208,400)	(19,245,100)
Total liabilities and equity	$ (38,063,200)	$ (33,784,200)

SUPPLEMENTAL CONDENSED CONSOL_5

SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION CONDENSED CONSOLIDATING FINANCIAL STATEMENTS, Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Cash provided by operating activities	$ 1,946,779	$ 2,186,719	$ 1,315,412
Investing activities
Capital expenditures	(3,848,349)	(2,141,475)	(512,393)
Contributions to unconsolidated affiliates	(4,028)	(1,748)	(87,861)
Other investing activities	(10,549)	1,578	3,879
Cash used in investing activities	(3,768,758)	(2,114,888)	(567,633)
Financing activities
Dividends paid	(1,457,628)	(1,335,058)	(829,414)
Distributions to noncontrolling interests	0	(3,500)	(276,260)
Borrowing (repayment) of short-term borrowings, net	220,000	(614,673)	(495,604)
Issuance of long-term debt, net of discounts	4,185,435	1,795,773	1,190,496
Debt financing costs	(29,747)	(13,441)	(11,425)
Repayment of long-term debt	(1,057,348)	(932,650)	(994,776)
Issuance of common stock	29,040	1,203,981	471,358
Acquisition of noncontrolling interests	0	(195,000)	0
Other, net	(58,790)	(2,481)	(13,836)
Cash provided by (used in) financing activities	1,830,962	(97,049)	(959,461)
Change in cash and cash equivalents	8,983	(25,218)	(211,682)
Cash and cash equivalents at beginning of period	11,975	37,193	248,875
Cash and cash equivalents at end of period	20,958	11,975	37,193
Reportable Legal Entities | Parent Issuer & Guarantor
Operating activities
Cash provided by operating activities	1,010,100	1,325,100	947,400
Investing activities
Capital expenditures	(25,600)	(18,800)	0
Contributions to unconsolidated affiliates			0
Other investing activities	0	0	0
Cash used in investing activities	(25,600)	(18,800)	0
Financing activities
Dividends paid	(1,457,600)	(1,335,100)	(829,400)
Distributions to noncontrolling interests		0	0
Intercompany borrowings (advances), net	(3,618,600)	(2,154,400)	(2,500,700)
Borrowing (repayment) of short-term borrowings, net	220,000	(614,700)	614,700
Issuance of long-term debt, net of discounts	4,185,400	1,795,800	1,190,500
Repayment of long-term debt	(249,600)	0	(87,100)
Issuance of common stock	29,000	1,204,000	471,400
Acquisition of noncontrolling interests		(195,000)
Other, net	(84,100)	(32,100)	(18,100)
Cash provided by (used in) financing activities	(975,500)	(1,331,500)	(1,158,700)
Change in cash and cash equivalents	9,000	(25,200)	(211,300)
Cash and cash equivalents at beginning of period	12,000	37,200	248,500
Cash and cash equivalents at end of period	21,000	12,000	37,200
Reportable Legal Entities | Subsidiary Issuer & Guarantor
Operating activities
Cash provided by operating activities	1,332,900	1,344,700	1,348,300
Investing activities
Capital expenditures	0	0	0
Contributions to unconsolidated affiliates			0
Other investing activities	0	0	0
Cash used in investing activities	0	0	0
Financing activities
Dividends paid	(1,332,000)	(1,332,000)	(1,332,000)
Distributions to noncontrolling interests		0	0
Intercompany borrowings (advances), net	801,800	912,300	2,001,200
Borrowing (repayment) of short-term borrowings, net	0	0	(1,110,300)
Issuance of long-term debt, net of discounts	0	0	0
Repayment of long-term debt	(800,000)	(925,000)	(900,000)
Issuance of common stock	0	0	0
Acquisition of noncontrolling interests		0
Other, net	(2,700)	0	(7,200)
Cash provided by (used in) financing activities	(1,332,900)	(1,344,700)	(1,348,300)
Change in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	0	0	0
Reportable Legal Entities | Guarantor Subsidiary
Operating activities
Cash provided by operating activities	68,900	67,900	59,000
Investing activities
Capital expenditures	0	0	0
Contributions to unconsolidated affiliates			(83,000)
Other investing activities	74,600	15,300	14,800
Cash used in investing activities	74,600	15,300	(68,200)
Financing activities
Dividends paid	(1,332,000)	(1,332,000)	(1,332,000)
Distributions to noncontrolling interests		0	0
Intercompany borrowings (advances), net	1,188,500	1,248,800	1,340,800
Borrowing (repayment) of short-term borrowings, net	0	0	0
Issuance of long-term debt, net of discounts	0	0	0
Repayment of long-term debt	0	0	0
Issuance of common stock	0	0	0
Acquisition of noncontrolling interests		0
Other, net	0	0	0
Cash provided by (used in) financing activities	(143,500)	(83,200)	8,800
Change in cash and cash equivalents	0	0	(400)
Cash and cash equivalents at beginning of period	0	0	400
Cash and cash equivalents at end of period	0	0	0
Reportable Legal Entities | Combined Non-Guarantor Subsidiaries
Operating activities
Cash provided by operating activities	2,198,900	2,113,000	1,353,700
Investing activities
Capital expenditures	(3,822,700)	(2,122,700)	(512,400)
Contributions to unconsolidated affiliates			(4,900)
Other investing activities	4,900	11,300	17,900
Cash used in investing activities	(3,817,800)	(2,111,400)	(499,400)
Financing activities
Dividends paid	0	0	0
Distributions to noncontrolling interests		(3,500)	(5,300)
Intercompany borrowings (advances), net	1,628,300	(6,700)	(841,300)
Borrowing (repayment) of short-term borrowings, net	0	0	0
Issuance of long-term debt, net of discounts	0	0	0
Repayment of long-term debt	(7,700)	(7,700)	(7,700)
Issuance of common stock	0	0	0
Acquisition of noncontrolling interests		0
Other, net	(1,700)	16,300	0
Cash provided by (used in) financing activities	1,618,900	(1,600)	(854,300)
Change in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	0	0	0
Reportable Legal Entities | Total
Operating activities
Cash provided by operating activities	1,946,800	2,186,700	1,315,400
Investing activities
Capital expenditures	(3,848,300)	(2,141,500)	(512,400)
Contributions to unconsolidated affiliates			(87,900)
Other investing activities	79,500	26,600	32,700
Cash used in investing activities	(3,768,800)	(2,114,900)	(567,600)
Financing activities
Dividends paid	(1,457,600)	(1,335,100)	(829,400)
Distributions to noncontrolling interests		(3,500)	(276,300)
Intercompany borrowings (advances), net	0	0	0
Borrowing (repayment) of short-term borrowings, net	220,000	(614,700)	(495,600)
Issuance of long-term debt, net of discounts	4,185,400	1,795,800	1,190,500
Repayment of long-term debt	(1,057,300)	(932,700)	(994,800)
Issuance of common stock	29,000	1,204,000	471,400
Acquisition of noncontrolling interests		(195,000)
Other, net	(88,500)	(15,800)	(25,300)
Cash provided by (used in) financing activities	1,831,000	(97,000)	(959,500)
Change in cash and cash equivalents	9,000	(25,200)	(211,700)
Cash and cash equivalents at beginning of period	12,000	37,200	248,900
Cash and cash equivalents at end of period	21,000	12,000	37,200
Consolidating Entries and Other
Operating activities
Cash provided by operating activities	(2,664,000)	(2,664,000)	(2,393,000)
Investing activities
Capital expenditures	0	0	0
Contributions to unconsolidated affiliates			0
Other investing activities	0	0	0
Cash used in investing activities	0	0	0
Financing activities
Dividends paid	2,664,000	2,664,000	2,664,000
Distributions to noncontrolling interests		0	(271,000)
Intercompany borrowings (advances), net	0	0	0
Borrowing (repayment) of short-term borrowings, net	0	0	0
Issuance of long-term debt, net of discounts	0	0	0
Repayment of long-term debt	0	0	0
Issuance of common stock	0	0	0
Acquisition of noncontrolling interests		0
Other, net	0	0	0
Cash provided by (used in) financing activities	2,664,000	2,664,000	2,393,000
Change in cash and cash equivalents	0	0	0
Cash and cash equivalents at beginning of period	0	0	0
Cash and cash equivalents at end of period	$ 0	$ 0	$ 0