Tallgrass Energy 10-Q 31 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document Information [Line Items]
Entity Registrant Name	TALLGRASS ENERGY, LP
Entity Central Index Key	1,633,651
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q3
Trading Symbol	TGE
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Capital Unit, Class A
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		156,308,654
Capital Unit, Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		123,887,893

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets:
Cash and cash equivalents	$ 5,521	$ 2,593
Accounts receivable, net	235,700	118,615
Receivable from related parties	3,369	1,340
Inventories	29,317	21,609
Prepayments and other current assets	16,344	13,165
Total Current Assets	290,251	157,322
Property, plant and equipment, net	2,662,055	2,394,337
Goodwill	404,838	404,838
Intangible assets, net	132,826	97,731
Unconsolidated investments	1,872,879	909,531
Deferred financing costs, net	11,778	12,563
Deferred tax asset	291,886	312,997
Deferred charges and other assets	3,527	2,694
Total Assets	5,670,040	4,292,013
Current Liabilities:
Accounts payable	223,148	98,882
Accounts payable to related parties	0	5,342
Accrued taxes	25,437	19,272
Accrued interest	12,523	25,167
Accrued liabilities	18,032	10,540
Deferred revenue	103,652	88,471
Other current liabilities	14,409	11,202
Total Current Liabilities	397,201	258,876
Long-term debt, net	3,033,674	2,292,993
Other long-term liabilities and deferred credits	20,117	18,965
Total Long-term Liabilities	3,053,791	2,311,958
Commitments and Contingencies
Equity [Abstract]
Total Partners' Equity	1,738,245	48,613
Noncontrolling interests (inclusive of Class B Exchange Right Holders)	480,803	1,672,566
Total Equity	2,219,048	1,721,179
Total Liabilities and Equity	5,670,040	4,292,013
Common Class A
Equity [Abstract]
Total Partners' Equity	1,738,245	48,613
Common Class B
Equity [Abstract]
Total Partners' Equity	$ 0	$ 0

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - shares	Sep. 30, 2018	Dec. 31, 2017
Common Class A
Shares, Outstanding	155,887,756	58,085,002
Common Class B
Shares, Outstanding	124,305,459	99,154,440

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total Revenues	$ 200,320,000	$ 175,869,000	$ 573,003,000	$ 481,132,000
Operating Costs and Expenses:
Operations and maintenance	18,011,000	17,412,000	52,850,000	45,569,000
Depreciation and amortization	27,595,000	23,782,000	81,408,000	67,276,000
General and administrative	16,015,000	16,489,000	53,526,000	46,040,000
Taxes, other than income taxes	7,750,000	6,661,000	25,091,000	21,799,000
Gain on disposal of assets	279,000	0	9,417,000	1,264,000
Total Operating Costs and Expenses	110,236,000	101,866,000	321,731,000	276,959,000
Operating Income	90,084,000	74,003,000	251,272,000	204,173,000
Other Income (Expense):
Equity in earnings of unconsolidated investments	76,268,000	123,642,000	222,857,000	187,121,000
Interest expense, net	(34,019,000)	(24,408,000)	(95,062,000)	(61,539,000)
Other (expense) income, net	(1,624,000)	10,182,000	(843,000)	12,409,000
Total Other Income (Expense)	40,625,000	109,416,000	126,952,000	137,991,000
Net income before tax	130,709,000	183,419,000	378,224,000	342,164,000
Deferred income tax expense	11,997,000	12,642,000	35,498,000	24,982,000
Net income	118,712,000	170,777,000	342,726,000	317,182,000
Net income attributable to noncontrolling interests	(59,162,000)	(154,911,000)	(265,378,000)	(280,534,000)
Net income attributable to TGE	$ 59,550,000	$ 15,866,000	$ 77,348,000	$ 36,648,000
Earnings Per Share, Basic and Diluted [Abstract]
Basic net income per Class A share	$ 0.38	$ 0.27	$ 0.85	$ 0.63
Diluted net income per Class A share	$ 0.38	$ 0.27	$ 0.85	$ 0.63
Basic average number of Class A shares outstanding	155,001	58,075	91,183	58,075
Diluted average number of Class A shares outstanding	156,088	58,192	92,661	58,193
Crude oil transportation services
Revenues:
Total Revenues	$ 100,226,000	$ 86,180,000	$ 286,130,000	$ 260,366,000
Natural gas transportation services
Revenues:
Total Revenues	30,953,000	30,256,000	94,623,000	91,370,000
Sales of natural gas, NGLs, and crude oil
Revenues:
Total Revenues	44,072,000	32,215,000	119,467,000	70,514,000
Processing and other revenues
Revenues:
Total Revenues	25,069,000	27,218,000	72,783,000	58,882,000
Cost of Sales
Operating Costs and Expenses:
Cost of sales and transportation services	28,556,000	26,984,000	82,601,000	58,740,000
Cost of transportation services
Operating Costs and Expenses:
Cost of sales and transportation services	$ 12,588,000	$ 10,538,000	$ 35,672,000	$ 38,799,000

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (UNAUDITED) - USD ($)	Total	Tallgrass Energy Partners	Pony Express Pipeline	Noncontrolling Interest	Noncontrolling InterestTallgrass Energy Partners	Noncontrolling InterestPony Express Pipeline	Noncontrolling InterestTerminals and NatGas	Noncontrolling InterestRockies Express Pipeline LLC	Noncontrolling InterestDeeprock Development, LLC	Noncontrolling InterestWater Solutions	Total Partner Equity Including Portion Attributable to Noncontrolling Interest	Total Partner Equity Including Portion Attributable to Noncontrolling InterestTallgrass Energy Partners	Total Partner Equity Including Portion Attributable to Noncontrolling InterestPony Express Pipeline	Total Partner Equity Including Portion Attributable to Noncontrolling InterestTerminals and NatGas	Total Partner Equity Including Portion Attributable to Noncontrolling InterestRockies Express Pipeline LLC	Total Partner Equity Including Portion Attributable to Noncontrolling InterestDeeprock Development, LLC	Total Partner Equity Including Portion Attributable to Noncontrolling InterestWater Solutions	Predecessor Equity	Predecessor EquityTallgrass Energy Partners	Predecessor EquityPony Express Pipeline	Predecessor EquityTerminals and NatGas	Predecessor EquityRockies Express Pipeline LLC	Predecessor EquityDeeprock Development, LLC	Predecessor EquityWater Solutions	Capital Unit, Class BNoncontrolling Interest	Capital Unit, Class BTotal Partner Equity Including Portion Attributable to Noncontrolling Interest	Capital Unit, Class ATotal Partner Equity Including Portion Attributable to Noncontrolling Interest	Common Class A	Common Class ATallgrass Energy Partners	Common Class APony Express Pipeline	Common Class ATerminals and NatGas	Common Class ARockies Express Pipeline LLC	Common Class ADeeprock Development, LLC	Common Class AWater Solutions	Common Class ACapital Unit, Class A	Common Class B	Common Class BTallgrass Energy Partners	Common Class BPony Express Pipeline	Common Class BTerminals and NatGas	Common Class BRockies Express Pipeline LLC	Common Class BDeeprock Development, LLC	Common Class BWater Solutions	Tallgrass Development LPNoncontrolling InterestTallgrass Energy Partners	Tallgrass Development LPTotal Partner Equity Including Portion Attributable to Noncontrolling InterestTallgrass Energy Partners	Tallgrass Development LPCommon Class ATallgrass Energy Partners
Partners' Capital, Including Portion Attributable to Noncontrolling Interest				$ 1,596,152,000							$ 1,929,414,000							$ 82,295,000										$ 250,967,000								$ 0
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 317,182,000			280,534,000							317,182,000							0										36,648,000								0
Dividends paid to Class A shareholders				0							(52,704,000)							0										(52,704,000)								0
Noncash compensation expense				6,169,000							7,355,000							0										1,186,000								0
Acquisitions							$ (36,391,000)	$ 40,159,000	$ 45,869,000					$ (140,000,000)	$ 63,681,000	$ 45,869,000					$ (82,295,000)	$ 0	$ 0								$ (21,314,000)	$ 23,522,000	$ 0						$ 0	$ 0	$ 0
Contributions from noncontrolling interest				1,093,000							1,093,000							0										0								0
Distributions to noncontrolling interest	(229,710,000)		$ 0	(229,710,000)							(229,710,000)							0										0								0
Issuance of TEP common units to the public, net of offering costs		$ 112,400,000			$ 101,043,000							$ 112,393,000							$ 0										$ 11,350,000								$ 0
TEP LTIP units tendered by employees to satisfy tax withholding obligations					(11,139,000)							(12,402,000)							0										(1,263,000)								0
Partial exercise of call option				(72,890,000)							(84,942,000)							0										(12,052,000)								0
Payments for Repurchase of Common Stock		35,335,000			(31,717,000)							(35,335,000)							0										(3,618,000)								0
Contributions from TD				1,451,000							2,301,000							0										850,000								0
Payments to Acquire Additional Interest in Subsidiaries										$ 7,109,000							$ 6,440,000							$ 0										$ (669,000)								$ 0
Partners' Capital, Including Portion Attributable to Noncontrolling Interest				1,683,514,000							1,917,755,000							0										234,241,000								0
Partners' Capital, Including Portion Attributable to Noncontrolling Interest	1,721,179,000			1,672,566,000							1,721,179,000							0										48,613,000								0
Cumulative effect of ASC 606 implementation | Accounting Standards Update 2014-09								39,543,000							44,131,000							0										4,588,000								0
Net income	342,726,000			265,378,000							342,726,000							0										77,348,000								0
Dividends paid to Class A shareholders				0							(126,714,000)							0										(126,714,000)								0
Noncash compensation expense				3,197,000							5,575,000							0										2,378,000								0
Issuance of Tallgrass Equity units																									$ 644,782,000	$ 644,782,000
Acquisitions						$ (44,732,000)		$ 74,421,000					$ (50,000,000)		$ 108,537,000					$ 0		$ 0								$ (5,268,000)		$ 34,116,000						$ 0		$ 0
Consolidation of Deeprock North									$ 31,843,000							$ 31,843,000							$ 0										$ 0
Contributions from noncontrolling interest				183,000							183,000							0										0								0
Distributions to noncontrolling interest	(262,856,000)		$ (50,000,000)	(262,856,000)							(262,856,000)							0																		0
Issuance of TEP common units to the public, net of offering costs					(279,000)							(377,000)							$ 0										(98,000)								0
TEP LTIP units tendered by employees to satisfy tax withholding obligations					1,531,000							(1,721,000)																	190,000								$ 0
Conversion of Class B shares to Class A shares																									$ 10,135,000										$ (10,135,000)
Deferred tax asset				0							13,503,000																	13,503,000								0
Other Significant Noncash Transaction, Payments to Acquire Units					$ 1,762,327,000							$ 2,113,758,000																	$ 351,431,000														$ 189,520,000	$ 251,743,000	$ 62,223,000
Issuance of Class A shares																											$ 2,113,758,000								$ 2,113,758,000
Payments for Repurchase of Common Stock		$ 0
Partners' Capital, Including Portion Attributable to Noncontrolling Interest	$ 2,219,048,000			$ 480,803,000							$ 2,219,048,000							$ 0										$ 1,738,245,000								$ 0

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 342,726,000	$ 317,182,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	86,121,000	73,087,000
Equity in earnings of unconsolidated investments	(222,857,000)	(187,121,000)
Distributions from unconsolidated investments	222,082,000	187,624,000
Deferred income tax expense	35,498,000	24,982,000
Other noncash items, net	(4,681,000)	(6,772,000)
Changes in components of working capital
Accounts receivable and other	(115,330,000)	(34,189,000)
Accounts payable and accrued liabilities	104,920,000	42,680,000
Deferred revenue	14,265,000	26,898,000
Other current assets and liabilities	1,682,000	5,032,000
Other operating, net	1,965,000	974,000
Net Cash Provided by Operating Activities	466,391,000	450,377,000
Cash Flows from Investing Activities:
Payments to acquire equity method investments	(444,788,000)	(31,570,000)
Capital expenditures	(265,073,000)	(88,050,000)
Acquisitions	(95,000,000)	(57,202,000)
Distributions from unconsolidated investments in excess of cumulative earnings	60,720,000	41,886,000
Sale of Tallgrass Crude Gathering	50,046,000
Acquisition of Rockies Express membership interest	0	(400,000,000)
Payments to Acquire Businesses, Gross	0
Payments to Acquire Assets, Investing Activities	0	128,526,000
Other investing, net	(12,304,000)	(13,449,000)
Net Cash Used in Investing Activities	(756,499,000)	(852,941,000)
Net Cash Provided by Financing Activities
Proceeds from issuance of long-term debt	500,000,000	850,000,000
Distributions to noncontrolling interests	(262,856,000)	(229,710,000)
Borrowings (repayments) under revolving credit facilities, net	244,000,000	(136,000,000)
Dividends paid to Class A shareholders	(126,714,000)	(52,704,000)
Proceeds from public offering of TEP common units, net of offering costs	0	112,393,000
Other financing, net	(11,394,000)	(32,879,000)
Net Cash Provided by Financing Activities	293,036,000	403,384,000
Net Change in Cash and Cash Equivalents
Net Change in Cash and Cash Equivalents	2,928,000	820,000
Cash and Cash Equivalents, beginning of period	2,593,000	2,459,000
Cash and Cash Equivalents, end of period	5,521,000	3,279,000
Supplemental Cash Flow Disclosures
Issuance of Shares	644,782,000	6,617,000
Contribution of 38% membership interest in Deeprock North to Deeprock Development	(19,500,000)
Issuance of noncontrolling interests in Deeprock Development in exchange for 62% membership interest in Deeprock North	(31,843,000)
Increase in Accrual for Property Plant and Equipment	8,517,000	1,342,000
Terminals and NatGas
Cash Flows from Investing Activities:
Payments to Acquire Businesses, Gross		(140,000,000)
Tallgrass Crude Gathering, LLC
Cash Flows from Investing Activities:
Payments to Acquire Businesses, Gross	0	(36,030,000)
Tallgrass Energy Partners
Net Cash Provided by Financing Activities
Payments for Repurchase of Common Stock	0	(35,335,000)
Supplemental Cash Flow Disclosures
Other Significant Noncash Transaction, Value of Consideration Given	(2,365,501,000)
Pony Express Pipeline
Net Cash Provided by Financing Activities
Distributions to noncontrolling interests	(50,000,000)	0
Rockies Express Pipeline LLC
Supplemental Cash Flow Disclosures
Other Significant Noncash Transaction, Value of Consideration Given	(393,039,000)
Equity Option
Net Cash Provided by Financing Activities
Payments for Repurchase of Common Stock	0	$ (72,381,000)
Capital Unit, Class A
Supplemental Cash Flow Disclosures
Issuance of Shares	2,113,758,000
Pawnee Terminal, LLC
Cash Flows from Investing Activities:
Payments to acquire equity method investments	(30,600,000)
Deeprock North, LLC
Cash Flows from Investing Activities:
Payments to acquire equity method investments	$ (19,500,000)

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Tallgrass Energy, LP ("TGE"), formerly known as Tallgrass Energy GP, LP, is a limited partnership that owns, operates, acquires and develops midstream energy assets in North America and has elected to be treated as a corporation for U.S. federal income tax purposes. "We," "us," "our" and similar terms refer to TGE together with its consolidated subsidiaries. Our operations are conducted through, and our operating assets are owned by, our direct and indirect subsidiaries, including Tallgrass Equity, LLC ("Tallgrass Equity"), in which we directly own an approximate 55.64% membership interest as of September 30, 2018 . We are located in and provide services to certain key United States hydrocarbon basins, including the Denver-Julesburg, Powder River, Wind River, Permian and Hugoton-Anadarko Basins and the Niobrara, Mississippi Lime, Eagle Ford, Bakken, Marcellus, and Utica shale formations. Our reportable business segments are: • Natural Gas Transportation—the ownership and operation of FERC-regulated interstate natural gas pipelines and an integrated natural gas storage facility; • Crude Oil Transportation—the ownership and operation of a FERC-regulated crude oil pipeline system; and • Gathering, Processing & Terminalling—the ownership and operation of natural gas gathering and processing facilities; crude oil storage and terminalling facilities; the provision of water business services primarily to the oil and gas exploration and production industry; the transportation of NGLs; and the marketing of crude oil and NGLs. Natural Gas Transportation. We provide natural gas transportation and storage services for customers in the Rocky Mountain, Midwest and Appalachian regions of the United States through: (1) our 75% membership interest in Rockies Express Pipeline LLC ("Rockies Express"), which owns the Rockies Express Pipeline, a FERC-regulated natural gas pipeline system extending from Opal, Wyoming and Meeker, Colorado to Clarington, Ohio (the "Rockies Express Pipeline"), and our 100% membership interest in Tallgrass NatGas Operator, LLC ("NatGas"), which operates the Rockies Express Pipeline, (2) the Tallgrass Interstate Gas Transmission system, a FERC-regulated natural gas transportation and storage system located in Colorado, Kansas, Missouri, Nebraska and Wyoming (the "TIGT System"), and (3) the Trailblazer Pipeline system, a FERC-regulated natural gas pipeline system extending from the Colorado and Wyoming border to Beatrice, Nebraska (the "Trailblazer Pipeline"). Crude Oil Transportation. We provide crude oil transportation to customers in Wyoming, Colorado, Kansas, and the surrounding regions through Tallgrass Pony Express Pipeline, LLC ("Pony Express"), which owns a FERC-regulated crude oil pipeline commencing in both Guernsey, Wyoming and Weld County, Colorado and terminating in Cushing, Oklahoma (the "Pony Express System"). In the second quarter of 2018, Pony Express placed into service an extension of the system from an additional origin point in Weld County, Colorado located near Platteville, Colorado. Gathering, Processing & Terminalling. We provide natural gas gathering and processing services for customers in Wyoming through: (1) a natural gas gathering system in the Powder River Basin (the "Douglas Gathering System"), (2) natural gas processing facilities in Casper and Douglas, and (3) a natural gas treating facility at West Frenchie Draw. We also provide NGL transportation services in Northeast Colorado and Wyoming. We perform water business services, including freshwater transportation and produced water gathering and disposal, in Colorado, Texas, Wyoming, and North Dakota through BNN Water Solutions, LLC ("Water Solutions"), and crude oil storage and terminalling services through our 100% membership interest in Tallgrass Terminals, LLC ("Terminals"), which owns and operates crude oil terminals in Colorado, Oklahoma, and Kansas . The Gathering, Processing & Terminalling segment also includes Stanchion Energy, LLC ("Stanchion"), which transacts in crude oil. The term "Terminals Predecessor" refers to Terminals and the term "NatGas Predecessor" refers to NatGas prior to their acquisition by TEP on January 1, 2017. Terminals Predecessor and NatGas Predecessor are collectively referred to as the Predecessor Entities. Financial results for all prior periods have been recast to reflect the operations of the Predecessor Entities. Predecessor Equity as presented in the condensed consolidated financial statements represents the capital account activity of Terminals Predecessor and NatGas Predecessor prior to January 1, 2017. Merger Agreement with Tallgrass Energy Partners, LP TGE previously entered into a definitive Agreement and Plan of Merger, dated as of March 26, 2018 (the "Merger Agreement"), with Tallgrass Equity, Tallgrass Energy Partners, LP, a Delaware limited partnership ("TEP"), Tallgrass MLP GP, LLC, a Delaware limited liability company and the general partner of TEP ("TEP GP"), and Razor Merger Sub, LLC, a Delaware limited liability company. The merger transaction contemplated by the Merger Agreement (the "TEP Merger") was completed effective June 30, 2018, and as a result, 47,693,097 TEP common units held by the public were converted into the right to receive Class A shares of TGE at an exchange ratio of 2.0 Class A shares for each outstanding TEP common unit, TEP's incentive distribution rights were cancelled, TEP's common units are no longer publicly traded, and 100% of TEP's equity interests are now owned by Tallgrass Equity and its subsidiaries. The TEP Merger was accounted for as an acquisition of noncontrolling interest. Following consummation of the TEP Merger, TGE changed its name from "Tallgrass Energy GP, LP" to "Tallgrass Energy, LP" and began trading on the New York Stock Exchange under the ticker symbol "TGE" on July 2, 2018.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Basis of Presentation These condensed consolidated financial statements and related notes for the three and nine months ended September 30, 2018 and 2017 were prepared in accordance with the accounting principles contained in the Financial Accounting Standards Board's Accounting Standards Codification, the single source of accounting principles generally accepted in the United States of America ("GAAP") for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by GAAP for annual periods. The condensed consolidated financial statements for the three and nine months ended September 30, 2018 and 2017 include all normal, recurring adjustments and disclosures that we believe are necessary for a fair statement of the results for the interim periods. In this report, the Financial Accounting Standards Board is referred to as the FASB and the FASB Accounting Standards Codification is referred to as the Codification or ASC. Certain prior period amounts have been reclassified to conform to the current presentation. Our financial results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2018 . The accompanying condensed consolidated interim financial statements should be read in conjunction with our audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2017 ("2017 Form 10-K") filed with the SEC on February 13, 2018. The condensed consolidated financial statements include the accounts of TGE and its subsidiaries and controlled affiliates. Significant intra-entity items have been eliminated in the presentation. Net income or loss from consolidated subsidiaries that are not wholly-owned by TGE is attributed to TGE and noncontrolling interests in accordance with the respective ownership interests. A variable interest entity ("VIE") is a legal entity that possesses any of the following characteristics: an insufficient amount of equity at risk to finance its activities, equity owners who do not have the power to direct the significant activities of the entity (or have voting rights that are disproportionate to their ownership interest), or equity owners who do not have the obligation to absorb expected losses or the right to receive the expected residual returns of the entity. Companies are required to consolidate a VIE if they are its primary beneficiary, which is the enterprise that has a variable interest that could be significant to the VIE and the power to direct the activities that most significantly impact the entity's economic performance. We have presented separately in our condensed consolidated balance sheets, to the extent material, the liabilities of our consolidated VIEs for which creditors do not have recourse to our general credit. Our consolidated VIEs did not have material assets that could only be used to settle specific obligations of the consolidated VIEs. Prior to June 29, 2018, both Tallgrass Equity and TEP were considered to be VIEs under the applicable authoritative guidance and included in our consolidated results. As a result of the TEP Merger, and changes in ownership and their respective partnership arrangements, Tallgrass Equity and TEP are no longer considered to be VIEs. We continue to consolidate our membership interests in Tallgrass Equity and TEP through the voting interest model. Use of Estimates Certain amounts included in or affecting these condensed consolidated financial statements and related disclosures must be estimated, requiring management to make certain assumptions with respect to values or conditions which cannot be known with certainty at the time the financial statements are prepared. These estimates and assumptions affect the amounts reported for assets, liabilities, revenues, and expenses during the reporting period, and the disclosure of contingent assets and liabilities at the date of the financial statements. Management evaluates these estimates on an ongoing basis, utilizing historical experience, consultation with experts and other methods it considers reasonable in the particular circumstances. Nevertheless, actual results may differ significantly from these estimates. Any effects on our business, financial position or results of operations resulting from revisions to these estimates are recorded in the period in which the facts that give rise to the revision become known. Accounting Pronouncement Recently Adopted Revenue Recognition In May 2014, the FASB issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 provides a comprehensive and converged set of principles-based revenue recognition guidelines which supersede the existing industry and transaction-specific standards. The core principle of the new guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, entities must apply a five-step process to (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 also mandates disclosure of sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The disclosure requirements include qualitative and quantitative information about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. Management completed its evaluation and implemented the revised guidance using the modified retrospective method as of January 1, 2018. This approach allows us to apply the new standard to (i) all new contracts entered into after January 1, 2018 and (ii) all existing contracts for which all (or substantially all) of the revenue has not been recognized under legacy revenue guidance as of January 1, 2018 through a cumulative adjustment to members' equity. Consolidated revenues presented in the comparative consolidated financial statements for periods prior to January 1, 2018 have not been revised. On January 1, 2018, we recorded a cumulative effect adjustment to equity of $44.1 million , increased the carrying amount of our investment in Rockies Express by $42.8 million , and recognized a receivable from Rockies Express of $1.3 million . These adjustments relate to the cumulative effect adjustment recorded by Rockies Express of $125.2 million upon adoption of ASC 606. The cumulative effect adjustment at Rockies Express arose as a result of the allocation of the transaction price to a series of individual performance obligations in certain long-term transportation contracts with tiered-pricing arrangements. The adjustment increases the carrying amount of our investment in Rockies Express to reflect increased equity in earnings and establishes a receivable for the increased management fee revenue that would have been earned by NatGas during the periods prior to implementation. Through our review process, we also identified the following changes to our revenue recognition policies that did not result in a cumulative effect adjustment on January 1, 2018: • Gathering & Processing. We have determined that a number of our gathering & processing contracts at TMID do not represent customer arrangements under ASC 606. Instead, arrangements deemed to represent wellhead purchases of raw gas will be accounted for as supply arrangements pursuant to ASC 705. As a result, gathering & processing fees previously recognized in revenue will be reported as a reduction to cost of sales under ASC 606. • Pipeline Loss Allowance. We have determined that pipeline loss allowance, or PLA, collected under certain crude oil transportation arrangements is a component of the transaction price where the PLA both significantly exceeds actual losses and was negotiated with the intent of providing a revenue stream to Pony Express. Under ASC 606, PLA barrels retained from customers will be subject to the guidance for noncash consideration and recognized in revenue at their contract inception fair value. See Note 12 – Revenue from Contracts with Customers for revenue disclosures related to both the implementation and the additional requirements prescribed by the standard. These new disclosures include information regarding the significant judgments used in evaluating when and how revenue is (or will be) recognized and data related to contract assets and liabilities. Accounting Pronouncements Not Yet Adopted ASU No. 2016-02, "Leases (Topic 842)" In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU 2016-02 provides a comprehensive update to the lease accounting topic in the Codification intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The amendments in ASU 2016-02 include a revised definition of a lease as well as certain scope exceptions. The changes primarily impact lessee accounting, while lessor accounting is largely unchanged from previous GAAP. Management is currently evaluating the impact of our pending adoption of ASC 842. The status of our implementation is as follows: • Management has formed an implementation team that meets to discuss implementation challenges, technical interpretations, industry-specific treatment of certain contract types, and project status. • Management is in the process of gathering data and reviewing contracts in order to identify all impacted contracts. • Management is evaluating the potential information technology and internal control changes that will be required for adoption based on the findings from its contract review process. • Management plans to provide internal training and awareness related to the revised guidance to the key stakeholders throughout its organization. The amendments in ASU 2016-02 are effective for public entities for annual reporting periods beginning after December 15, 2018, and for interim periods within that reporting period. Early application is permitted. We plan to adopt ASU 2016-02 on January 1, 2019 using the modified retrospective method. ASC 842 provides for a number of practical expedients. We intend to elect the following practical expedients upon adoption of ASC 842: • An entity need not reassess whether any expired or existing contracts are or contain leases. • An entity need not reassess the lease classification for any expired or existing leases. • An entity need not reassess initial direct costs for any existing leases. • An entity may elect to not assess whether existing or expired land easements that were not previously accounted for as leases are or contain a lease under ASC 842. While we are still in the process of quantifying the impact of adoption, we do not currently expect the adoption to have a material impact. We expect to recognize a right of use asset and lease liability at the implementation date, but we cannot reasonably estimate the full impact of the standard at this time. Additionally, we are currently evaluating our business processes, systems, and controls to ensure the accuracy and timeliness of the recognition and disclosure requirements under the new lease guidance.

Acquisitions & Dispositions

Acquisitions & Dispositions	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Acquisitions	Acquisition of Pawnee On January 2, 2018, we entered into an agreement to acquire a 51% membership interest in the Pawnee, Colorado crude oil terminal ("Pawnee") from Zenith Energy Terminals Holdings, LLC for cash consideration of approximately $30.6 million . The transaction closed on April 1, 2018. As the 51% membership interest does not represent a controlling interest in Pawnee, our investment in Pawnee is recorded under the equity method of accounting and reported as "Unconsolidated investments" on the condensed consolidated balance sheets. Acquisition of an Additional 25.01% Membership Interest in Rockies Express and Additional TEP Common Units In February 2018, Tallgrass Development, LP ("TD") merged into Tallgrass Development Holdings, LLC, a wholly-owned subsidiary of Tallgrass Equity ("Tallgrass Development Holdings"), and as a result of the merger, Tallgrass Equity acquired a 25.01% membership interest in Rockies Express and an additional 5,619,218 TEP common units. As consideration for the acquisition, TGE and Tallgrass Equity issued 27,554,785 unregistered TGE Class B shares and Tallgrass Equity units, valued at approximately $644.8 million based on the closing price on February 6, 2018, to the limited partners of TD. Subsequent to the closing of the transaction, our aggregate membership interest in Rockies Express is 75% . The transfer of the Rockies Express membership interest between TD and Tallgrass Equity is considered a transaction between entities under common control, but does not represent a change in reporting entity. As a result of the common control nature of the transaction, the acquisition resulted in the recognition of a noncash deemed contribution representing the excess carrying value of the 25.01% membership interest in Rockies Express acquired over the fair value of the consideration paid. For further discussion, see Note 11 - Partnership Equity . As the aggregate 75% membership interest does not represent a controlling interest in Rockies Express, TGE's investment in Rockies Express is recorded under the equity method of accounting and is reported as "Unconsolidated investments" on our condensed consolidated balance sheets. As a result of the common control nature of the transaction, the 25.01% membership interest in Rockies Express was transferred to Tallgrass Equity at TD's historical carrying amount, including the remaining unamortized basis difference driven by the difference between the fair value of the investment and the book value of the underlying assets and liabilities on November 13, 2012, the date of acquisition by TD. For additional information, see Note 7 - Investments in Unconsolidated Affiliates . The acquisition of an additional 5,619,218 TEP common units is considered an acquisition of noncontrolling interest and resulted in the recognition of a noncash deemed distribution representing the excess purchase price over the $53.8 million carrying value of the 5,619,218 TEP common units acquired as of February 7, 2018. For further discussion, see Note 11 - Partnership Equity . As of February 7, 2018, the negative basis difference in Rockies Express carried over from TD was approximately $376.5 million . The amount of the basis difference allocated to property, plant and equipment is accreted over 35 years , which equates to the 2.86% composite depreciation rate utilized by Rockies Express to depreciate the underlying property, plant and equipment. The amount allocated to long-term debt is amortized over the remaining life of the various debt facilities. At September 30, 2018 , the basis difference for our membership interests in Rockies Express was allocated as follows: Basis Difference Amortization Period (in thousands) Long-term debt $ 48,019 2 - 25 years Property, plant and equipment (1,156,562 ) 35 years Total basis difference $ (1,108,543 ) Sale of Tallgrass Crude Gathering In February 2018, we entered into an agreement with an affiliate of Silver Creek Midstream, LLC ("Silver Creek") to sell our 100% membership interest in Tallgrass Crude Gathering, LLC ("TCG"), which owns a 50 -mile crude oil gathering system in the Powder River Basin, for approximately $50.0 million . The sale of TCG closed on February 23, 2018. During the nine months ended September 30, 2018 , we recognized a gain of $9.4 million on the sale which is presented in the line item "Gain on disposal of assets" in the condensed consolidated statements of income. Joint Venture with Silver Creek In February 2018, we entered into an agreement with Silver Creek to form Iron Horse Pipeline, LLC ("Iron Horse"), a new joint venture pipeline to transport crude oil from the Powder River Basin. During the nine months ended September 30, 2018 , we contributed an initial $3.5 million and committed to funding our proportionate share of the remaining costs of construction in exchange for a 75% membership interest in Iron Horse. As the 75% membership interest does not represent a controlling interest in Iron Horse, our investment in Iron Horse is accounted for under the equity method of accounting and reported as "Unconsolidated investments" on the condensed consolidated balance sheets. In August 2018, we entered into an agreement with Silver Creek to expand the Iron Horse joint venture through the contribution by us and Silver Creek of additional Powder River Basin assets. Upon the closing of the additional contributions, the expanded joint venture will operate under the name Powder River Gateway, LLC, and will own the Iron Horse pipeline, the Powder River Express Pipeline, and crude oil terminal facilities in Guernsey, Wyoming. We will own a 51% membership interest and continue to operate the joint venture following closing, and Silver Creek will own a 49% membership interest. We expect to close the additional contributions in the fourth quarter of 2018, subject to certain closing conditions. Acquisition of Additional 2% Membership Interest in Pony Express In February 2018, we acquired the remaining 2% membership interest in Pony Express, along with administrative assets consisting primarily of information technology assets, from TD for cash consideration of approximately $60 million , bringing our aggregate membership interest in Pony Express to 100% . The acquisition of the remaining 2% membership interest in Pony Express represents a transaction between entities under common control and an acquisition of noncontrolling interests. As a result, financial information for periods prior to the transaction has not been recast to reflect the additional 2% membership interest. Acquisition of BNN North Dakota In January 2018, we acquired 100% of the membership interests in Buckhorn Energy Services, LLC and Buckhorn SWD Solutions, LLC, which were subsequently merged and renamed BNN North Dakota, LLC ("BNN North Dakota"), for approximately $95.0 million , net of cash acquired. BNN North Dakota owns a produced water gathering and disposal system in the Bakken basin with approximately 133,000 acres under dedication. The transaction qualifies as an acquisition of a business and is accounted for as a business combination under ASC 805. The following represents the fair value of assets acquired and liabilities assumed (in thousands): Accounts receivable $ 2,457 Inventory 67 Property, plant and equipment 48,900 Intangible asset 46,800 (1) Accounts payable and accrued liabilities (3,224 ) Net identifiable assets acquired (excluding cash) $ 95,000 (1) The $46.8 million intangible asset acquired represents three major customer relationships. This intangible asset is amortized on a straight-line basis over a period of 8 - 14 years, the remaining terms of the underlying contracts at the time of acquisition. At March 31, 2018, the assets acquired and liabilities assumed in the acquisition were recorded at provisional amounts based on the preliminary purchase price allocation. No adjustments were made to these provisional amounts and the allocation of assets acquired and liabilities assumed in the acquisition was considered final as of June 30, 2018. Actual revenue and net income attributable to TGE from BNN North Dakota of $13.3 million and $2.9 million , respectively, was recognized in the accompanying condensed consolidated statements of income for the period from January 12, 2018 to September 30, 2018 . Pro Forma Financial Information Unaudited pro forma revenue and net income attributable to TGE for the nine months ended September 30, 2018 and 2017 is presented below as if the acquisition of BNN North Dakota had been completed on January 1, 2017. Nine Months Ended September 30, 2018 2017 (in thousands) Revenue $ 573,431 $ 488,076 Net income attributable to TGE $ 77,374 $ 36,384 The pro forma financial information is not necessarily indicative of what the actual results of operations or financial position of TGE would have been if the transaction had in fact occurred on the date or for the period indicated, nor does it purport to project the results of operations or financial position of TGE for any future periods or as of any date. The pro forma financial information does not give effect to any cost savings, operating synergies, or revenue enhancements expected to result from the transaction or the costs to achieve these cost savings, operating synergies, and revenue enhancements. Acquisition of Deeprock North and Merger with Deeprock Development In January 2018, we acquired an approximate 38% membership interest in Deeprock North, LLC ("Deeprock North") from Kinder Morgan Deeprock North Holdco LLC for cash consideration of $19.5 million . Immediately following the acquisition, Deeprock North was merged into Deeprock Development, LLC ("Deeprock Development"), and the members of Deeprock North and Deeprock Development received adjusted membership interests in the combined entity. As a result, we recognized additional noncontrolling interests in Deeprock Development of $31.8 million . The acquisition of Deeprock North by Deeprock Development has been accounted for as an asset acquisition, with substantially all of the fair value allocated to the long-lived assets acquired based on their relative fair values. After the acquisition and merger, we own an approximate 60% membership interest in the combined entity.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	As a result of our relationship with Tallgrass Energy Holdings, LLC ("Tallgrass Energy Holdings") and its affiliates, we have entered into a number of related party transactions. The following disclosure includes those related party transactions which are not otherwise disclosed in these notes to our condensed consolidated financial statements. All of our employees are employed by Tallgrass Management, LLC ("Tallgrass Management"). Prior to July 1, 2018, Tallgrass Management was a wholly-owned subsidiary of Tallgrass Energy Holdings. In connection with the closing of the TEP initial public offering on May 17, 2013, TEP and TEP GP entered into an Omnibus Agreement with Tallgrass Energy Holdings and certain of its affiliates (the "TEP Omnibus Agreement"). The TEP Omnibus Agreement provides that, among other things, TEP will reimburse Tallgrass Energy Holdings and its affiliates for all expenses they incur and payments they make on TEP's behalf, including the costs of employee and director compensation and benefits as well as the cost of the provision of certain centralized corporate functions performed by Tallgrass Energy Holdings and its affiliates, including legal, accounting, cash management, insurance administration and claims processing, risk management, health, safety and environmental, information technology and human resources in each case to the extent reasonably allocable to TEP. In addition, in connection with the closing of the TGE initial public offering on May 12, 2015 (the "TGE IPO"), TGE entered into an Omnibus Agreement (the "TGE Omnibus Agreement") with Tallgrass Energy GP, LLC (formerly known as TEGP Management, LLC), Tallgrass Equity and Tallgrass Energy Holdings. Effective July 1, 2018, Tallgrass Management was contributed to Tallgrass Equity in connection with the TEP Merger. As a result, the costs of employer and director compensation and benefits are now incurred directly by Tallgrass Equity. Totals of transactions with affiliated companies, excluding transactions disclosed elsewhere in these notes, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Processing and other revenues (1) $ 1,838 $ 3,338 $ 5,603 $ 6,662 Cost of transportation services (2) $ — $ 1,062 $ — $ 10,476 Charges to TGE: (3) Property, plant and equipment, net $ — $ 765 $ — $ 1,568 Operations and maintenance $ — $ 7,973 $ — $ 21,680 General and administrative $ — $ 11,960 $ — $ 32,628 (1) Reflects the fee that NatGas receives as the operator of the Rockies Express Pipeline. (2) Reflects rent expense for the crude oil storage at the Deeprock Terminal prior to our consolidation of Deeprock Development during the third quarter of 2017 . (3) Charges to TGE, inclusive of Tallgrass Equity and TEP, include indirectly charged wages and salaries, other compensation and benefits, and shared services for periods prior to January 1, 2018. Effective January 1, 2018, these costs are incurred by TEP directly and, in the case of certain employee compensation and benefits, paid on TEP's behalf by its affiliate, Tallgrass Management, LLC, pursuant to the TEP Omnibus Agreement. Details of balances with affiliates included in "Receivable from related parties" and "Accounts payable to related parties" in the condensed consolidated balance sheets are as follows: September 30, 2018 December 31, 2017 (in thousands) Receivable from related parties: Rockies Express Pipeline LLC $ 3,152 $ 1,340 Iron Horse Pipeline, LLC 112 — Pawnee Terminal, LLC 105 — Total receivable from related parties $ 3,369 $ 1,340 Accounts payable to related parties: Tallgrass Operations, LLC (1) $ — $ 5,342 Total accounts payable to related parties $ — $ 5,342 (1) Reflects accounts payable for charges to TGE, inclusive of Tallgrass Equity and TEP, including indirectly charged wages and salaries, other compensation and benefits, and shared services prior to January 1, 2018 as discussed above. Gas imbalances with affiliated shippers are as follows: September 30, 2018 December 31, 2017 (in thousands) Affiliate gas imbalance receivables $ 17 $ 18 Affiliate gas imbalance payables $ 689 $ 442

Inventory

Inventory	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Inventory	The components of inventory at September 30, 2018 and December 31, 2017 consisted of the following: September 30, 2018 December 31, 2017 (in thousands) Crude oil $ 18,893 $ 12,792 Materials and supplies 6,359 5,891 Natural gas liquids 364 942 Gas in underground storage 3,701 1,984 Total inventory $ 29,317 $ 21,609

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	A summary of net property, plant and equipment by classification is as follows: September 30, 2018 December 31, 2017 (in thousands) Crude oil pipelines $ 1,290,868 $ 1,220,379 Gathering, processing and terminalling assets (1) 791,766 675,092 Natural gas pipelines 612,729 581,400 General and other 125,261 98,680 Construction work in progress 198,356 97,978 Accumulated depreciation and amortization (356,925 ) (279,192 ) Total property, plant and equipment, net $ 2,662,055 $ 2,394,337 (1) Includes approximately $46.2 million and $40.1 million of assets associated with the acquisitions of Deeprock North and BNN North Dakota, respectively, in January 2018.

Investments in Unconsolidated A

Investments in Unconsolidated Affiliates - (Notes)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments and Joint Ventures Disclosure	Our investment in Rockies Express is recorded under the equity method of accounting and is reported as "Unconsolidated investments" on our condensed consolidated balance sheets. During the nine months ended September 30, 2018 , we recognized equity in earnings associated with our aggregate 75% membership interest in Rockies Express of $220.3 million , inclusive of the amortization of the negative basis difference, and received distributions from and made contributions to Rockies Express of $278.1 million and $420.3 million , respectively. As discussed in Note 3 – Acquisitions and Dispositions , we acquired an additional 25.01% membership interest in Rockies Express in February 2018. In July 2018, we made a special contribution of approximately $412.5 million to fund our portion of the repayment of Rockies Express' $550 million of 6.85% senior notes due July 15, 2018. Summarized financial information for Rockies Express is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Revenue $ 225,753 $ 216,756 $ 683,426 $ 625,243 Operating income $ 127,119 $ 123,965 $ 385,831 $ 344,037 Net income to Members $ 90,707 $ 233,990 $ 270,338 $ 371,185

Goodwill (Notes)

Goodwill (Notes)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill Disclosure	Reconciliation of Goodwill The following table presents a reconciliation of the carrying amount of goodwill by reportable segment for the reporting period: Three and Nine Months Ended September 30, 2018 2017 Natural Gas Transportation Gathering, Processing & Terminalling Total Natural Gas Transportation Gathering, Processing & Terminalling Total (in thousands) Balance at beginning of period $ 255,558 $ 149,280 $ 404,838 $ 255,558 $ 87,730 $ 343,288 Goodwill acquired — — — — 61,550 (1) 61,550 Balance at end of period $ 255,558 $ 149,280 $ 404,838 $ 255,558 $ 149,280 $ 404,838 (1) The $61.6 million of goodwill was recorded in connection with the acquisition of a controlling interest in Deeprock Development on July 20, 2017. Annual Goodwill Impairment Analysis We evaluate goodwill for impairment on an annual basis and whenever events or changes in circumstances necessitate an evaluation for impairment. Examples of such facts and circumstances include changes in the magnitude of the excess of fair value over carrying amount in the last valuation or changes in the business environment. Our annual impairment testing date is August 31. We evaluate goodwill for impairment at the reporting unit level, which is the same as, or one level below, an operating segment as defined in the segment reporting guidance of the Codification, using either the qualitative assessment option or proceeding directly to the quantitative impairment test depending on facts and circumstances of the reporting unit. For the purpose of goodwill impairment testing, goodwill was allocated to our reporting units based on the enterprise value of each reporting unit at the date of acquisition. If we, after performing the qualitative assessment, determine it is "more likely than not" that the fair value of a reporting unit is greater than its carrying amount, then goodwill is not considered impaired. When goodwill is evaluated for impairment using the quantitative impairment test, the carrying amount of the reporting unit is compared to its fair value. If the fair value exceeds the carrying amount, goodwill is not considered impaired. If the carrying amount exceeds the reporting unit's fair value, then the reporting unit should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. We elected to apply the qualitative assessment option for four of our five reporting units. In conducting the qualitative assessment we considered relevant factors and circumstances that affect the fair value or carrying amount of the reporting entity. Such factors included changes in discount rates, projected cash flows, macroeconomic considerations, industry and market considerations, overall financial performance, prior quantitative results, and entity and reporting unit specific events. For each of these reporting units, the results of the qualitative assessment indicated that it was more likely than not that the fair value of the reporting units exceeded their respective book values. As such, we did not perform a quantitative impairment analysis, and we concluded that no impairment was indicated as of August 31, 2018. We did not elect to apply the qualitative assessment option for one reporting unit during our 2018 annual goodwill impairment testing; instead we proceeded directly to the quantitative impairment test. We compared the fair value of the reporting unit with its respective book value, including goodwill, by using an income approach based on a discounted cash flow analysis. The fair value of the reporting unit was determined on a stand-alone basis from the perspective of a market participant and included a sensitivity analysis of the impact of changes in various assumptions. This approach required us to make long-term forecasts of future operating results and various other assumptions and estimates, the most significant of which are gross margin, operating expenses, general and administrative expenses, long-term growth rates, maintenance capital expenditures, and the weighted average cost of capital. The fair value of the reporting unit was determined using significant unobservable inputs, considered Level 3 under the fair value hierarchy in the Codification. For this reporting unit, the results of the quantitative impairment test indicated no impairment as the fair value of the reporting unit was greater than its respective book value. As a result, in accordance with the Codification guidance, we did not record a goodwill impairment during the nine months ended September 30, 2018 . Unpredictable events or deteriorating market or operating conditions could result in a future change to the discounted cash flow model and cause impairments in the future. We continue to monitor potential impairment indicators to determine if a triggering event occurs and will perform additional goodwill impairment analyses as necessary.

Risk Management

Risk Management	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Risk Management	We enter into derivative contracts with third parties for the purpose of hedging exposures that accompany our normal business activities. Our normal business activities directly and indirectly expose us to risks associated with changes in the market price of crude oil and natural gas, among other commodities. For example, the risks associated with changes in the market price of crude oil and natural gas include, among others (i) pre-existing or anticipated physical crude oil and natural gas sales, (ii) natural gas purchases and (iii) natural gas system use and storage. We have elected not to apply hedge accounting and changes in the fair value of all derivative contracts are recorded in earnings in the period in which the change occurs. Fair Value of Derivative Contracts The following table summarizes the fair values of our derivative contracts included in the condensed consolidated balance sheets: Balance Sheet September 30, 2018 December 31, 2017 (in thousands) Crude oil derivative contracts (1) Current assets $ 6,014 $ — Crude oil derivative contracts (2) Current liabilities $ 4,163 $ 2,368 (1) As of September 30, 2018 , the fair value shown for crude oil derivative contracts represents the forward purchase of 3,565,000 barrels which will settle throughout the fourth quarter of 2018 and 2019. (2) As of September 30, 2018 , the fair value shown for crude oil derivative contracts represents the forward sale of 3,163,500 barrels of crude oil which will settle throughout the fourth quarter of 2018 and 2019. As of December 31, 2017 , the fair value shown for crude oil derivative contracts represents the forward sale of 356,000 barrels of crude oil which settled in the first quarter of 2018. Effect of Derivative Contracts in the Statements of Income The following table summarizes the impact of derivative contracts not designated as hedging contracts for the three and nine months ended September 30, 2018 and 2017 : Location of gain (loss) recognized Amount of gain (loss) recognized in income on derivatives Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Crude oil derivative contracts Sales of natural gas, NGLs, and crude oil $ 9,435 $ 175 $ 16,665 $ 1,065 Natural gas derivative contracts Sales of natural gas, NGLs, and crude oil $ — $ (22 ) $ — $ 84 Call option derivative Other income, net $ — $ — $ — $ 1,885 Call Option Derivative As part of our acquisition of an additional 31.3% membership interest in Pony Express effective January 1, 2016, TD granted TEP an 18 month call option at an exercise price of $42.50 per TEP common unit covering the 6,518,000 TEP common units issued to TD as a portion of the consideration. On February 1, 2017 , we exercised the remainder of the call option covering an additional 1,703,094 TEP common units for a cash payment of $72.4 million . These TEP common units were deemed canceled upon the exercise of the call option and as of the applicable exercise date were no longer issued and outstanding. Credit Risk We have counterparty credit risk as a result of our use of derivative contracts. Counterparties to our commodity derivatives consist of market participants and major financial institutions. This concentration of counterparties may impact our overall exposure to credit risk, either positively or negatively, in that the counterparties may be similarly affected by changes in economic, regulatory or other conditions. The counterparty to our call option derivative was TD. Our derivative contracts are entered into with counterparties through central trading organizations such as futures, options or stock exchanges or counterparties outside of central trading organizations. While we typically enter into derivative transactions with investment grade counterparties and actively monitor their credit ratings, it is nevertheless possible that from time to time losses will result from counterparty credit risk in the future. The maximum potential exposure to credit losses on our crude oil derivative contracts at September 30, 2018 was: Asset Position (in thousands) Gross $ 6,014 Netting agreement impact — Cash collateral held — Net exposure $ 6,014 As of September 30, 2018 and December 31, 2017 , we had $1.1 million and $3.0 million , respectively, of cash in margin accounts and outstanding letters of credit in support of our commodity derivative contracts. Fair Value Derivative assets and liabilities are measured and reported at fair value. Derivative contracts can be exchange-traded or over-the-counter ("OTC"). OTC commodity derivatives are valued using models utilizing a variety of inputs including contractual terms and commodity and interest rate curves. The selection of a particular model and particular inputs to value an OTC derivative contract depends upon the contractual terms of the instrument as well as the availability of pricing information in the market. We use similar models to value similar instruments. For OTC derivative contracts that trade in liquid markets, such as generic forwards and swaps, model inputs can generally be verified and model selection does not involve significant management judgment. Such contracts are typically classified within Level 2 of the fair value hierarchy. The call option granted by TD was valued using a Black-Scholes option pricing model. Key inputs to the valuation model included the term of the option, risk free rate, the exercise price and current market price, expected volatility and expected distribution yield of the underlying units. The call option valuation was classified within Level 2 of the fair value hierarchy as the value was based on significant observable inputs. The following table summarizes the fair value measurements of our derivative contracts as of September 30, 2018 and December 31, 2017 , based on the fair value hierarchy: Asset Fair Value Measurements Using Total Quoted prices in Significant Significant (in thousands) As of September 30, 2018: Crude oil derivative contracts $ 6,014 $ — $ 6,014 $ — Liability Fair Value Measurements Using Total Quoted prices in Significant Significant (in thousands) As of September 30, 2018: Crude oil derivative contracts $ 4,163 $ — $ 4,163 $ — As of December 31, 2017: Crude oil derivative contracts $ 2,368 $ — $ 2,368 $ —

Long-term Debt

Long-term Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Long-term Debt	Long-term debt consisted of the following at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Tallgrass Equity revolving credit facility (1) $ — $ 146,000 TEP revolving credit facility 1,051,000 661,000 TEP 4.75% senior notes due October 1, 2023 500,000 — TEP 5.50% senior notes due September 15, 2024 750,000 750,000 TEP 5.50% senior notes due January 15, 2028 750,000 750,000 Less: Deferred financing costs, net (2) (20,793 ) (17,737 ) Plus: Unamortized premium on 2028 Notes 3,467 3,730 Total long-term debt, net $ 3,033,674 $ 2,292,993 (1) On July 26, 2018, Tallgrass Equity repaid all outstanding borrowings and terminated its revolving credit facility. (2) Deferred financing costs, net as presented above relate solely to the Senior Notes (as defined below). Deferred financing costs associated with our revolving credit facilities are presented in noncurrent assets on our condensed consolidated balance sheets. TEP Senior Unsecured Notes On September 26, 2018, TEP and Tallgrass Energy Finance Corp. (the "Co-Issuer" and together with TEP, the "Issuers"), the Guarantors named therein and U.S. Bank, National Association, as trustee, entered into an Indenture dated September 26, 2018 (the "2023 Indenture") pursuant to which the Issuers issued $500 million in aggregate principal amount of 4.75% senior notes due 2023 (the "2023 Notes"). The 2023 Indenture contains covenants that, among other things, limit TEP's ability and the ability of its restricted subsidiaries to: (i) create liens to secure indebtedness; (ii) enter into sale-leaseback transactions; and (iii) consolidate with or merge with or into, or sell substantially all TEP's properties to, another person. The Issuers have also previously issued $500 million in aggregate principal amount of 5.50% senior notes due 2028 (the "2028 Notes") on September 15, 2017 and an additional $250 million in aggregate principal amount of the 2028 Notes on December 11, 2017. The 2028 Notes issued on September 15, 2017 and December 11, 2017 are treated as a single class of debt securities and have identical terms, other than the issue date and offering price. The 2028 Notes are governed by an Indenture dated September 15, 2017 (the "2028 Indenture") which contains covenants that, among other things, limit TEP's ability and the ability of its restricted subsidiaries to: (i) create liens to secure indebtedness; (ii) enter into sale-leaseback transactions; and (iii) consolidate with or merge with or into, or sell substantially all TEP's properties to, another person. In addition, the Issuers have previously issued $400 million in aggregate principal amount of 5.50% senior notes due 2024 (the "2024 Notes") on September 1, 2016 and an additional $350 million in aggregate principal amount of the 2024 Notes on May 16, 2017. The 2024 Notes issued on September 1, 2016 and May 16, 2017 are treated as a single class of debt securities and have identical terms, other than the issue date, offering price and first interest payment date. The 2024 Notes are governed by an Indenture dated September 1, 2016 (the "2024 Indenture") which contains covenants that, among other things, limit TEP's ability and the ability of its restricted subsidiaries to: (i) incur, assume or guarantee additional indebtedness or issue preferred units; (ii) create liens to secure indebtedness; (iii) pay distributions on equity interests in the event of default or noncompliance with the covenants required, repurchase equity securities or redeem subordinated securities; (iv) make investments; (v) restrict distributions, loans or other asset transfers from TEP's restricted subsidiaries; (vi) consolidate with or merge with or into, or sell substantially all of TEP's properties to, another person; (vii) sell or otherwise dispose of assets, including equity interests in subsidiaries; and (viii) enter into transactions with affiliates. The 2023 Notes, 2024 Notes, and 2028 Notes are together referred to as the "Senior Notes." As of September 30, 2018 , TEP was in compliance with the covenants required under the 2023 Indenture, the 2024 Indenture, and the 2028 Indenture. TEP Revolving Credit Facility The following table sets forth the available borrowing capacity under the TEP revolving credit facility as of September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Total capacity under the TEP revolving credit facility $ 2,250,000 $ 1,750,000 Less: Outstanding borrowings under the TEP revolving credit facility (1,051,000 ) (661,000 ) Less: Letters of credit issued under the TEP revolving credit facility (94 ) (94 ) Available capacity under the TEP revolving credit facility $ 1,198,906 $ 1,088,906 On July 26, 2018, TEP and certain of its subsidiaries entered into Amendment No. 1 (the "Amendment") to its existing revolving credit facility with Wells Fargo Bank, National Association, as administrative agent and collateral agent, and a syndicate of lenders (the "Credit Agreement"). The Amendment modified certain provisions of the Credit Agreement to, among other things, (i) increase the available amount of the TEP revolving credit facility to $2.25 billion , (ii) reduce certain applicable margins in the pricing grids used to determine the interest rate and revolving credit commitment fees, (iii) modify the use of proceeds to allow TEP to pay off the Tallgrass Equity revolving credit facility, and (iv) increase the maximum total leverage ratio to 5.50 to 1.00. TEP's revolving credit facility contains various covenants and restrictive provisions that, among other things, limit or restrict TEP's ability (as well as the ability of its restricted subsidiaries) to incur or guarantee additional debt, incur certain liens on assets, dispose of assets, make certain distributions, including distributions from available cash, if a default or event of default under the credit agreement then exists or would result therefrom, change the nature of its business, engage in certain mergers or make certain investments and acquisitions, enter into non-arms-length transactions with affiliates and designate certain subsidiaries as "Unrestricted Subsidiaries." In addition, TEP is required to maintain a consolidated leverage ratio of not more than 5.50 to 1.00 ( 5.00 to 1.00 prior to the Amendment), a consolidated senior secured leverage ratio of not more than 3.75 to 1.00 and a consolidated interest coverage ratio of not less than 2.50 to 1.00. As of September 30, 2018 , TEP was in compliance with the covenants required under its revolving credit facility. The unused portion of TEP's revolving credit facility is subject to a commitment fee, which ranges from 0.250% to 0.375% ( 0.250% to 0.500% prior to the Amendment), based on TEP's total leverage ratio. As of September 30, 2018 , the weighted average interest rate on outstanding borrowings under the TEP revolving credit facility was 3.54% . During the nine months ended September 30, 2018 , the weighted average effective interest rate under the TEP revolving credit facility, including the interest on outstanding borrowings under TEP's revolving credit facility, commitment fees, and amortization of deferred financing costs, was 3.98% . Fair Value The following table sets forth the carrying amount and fair value of our long-term debt, which is not measured at fair value in the condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 , but for which fair value is disclosed: Fair Value Quoted prices Significant Significant Total Carrying (in thousands) As of September 30, 2018: Revolving credit facility $ — $ 1,051,000 $ — $ 1,051,000 $ 1,051,000 2023 Notes $ — $ 500,310 $ — $ 500,310 $ 495,637 2024 Notes $ — $ 766,635 $ — $ 766,635 $ 740,969 2028 Notes $ — $ 759,458 $ — $ 759,458 $ 746,068 As of December 31, 2017: Revolving credit facilities $ — $ 807,000 $ — $ 807,000 $ 807,000 2024 Notes $ — $ 771,645 $ — $ 771,645 $ 739,824 2028 Notes $ — $ 758,168 $ — $ 758,168 $ 746,169 The long-term debt borrowed under the revolving credit facilities is carried at amortized cost. As of September 30, 2018 and December 31, 2017 , the fair value of borrowings under the revolving credit facilities approximates the carrying amount of the borrowings using a discounted cash flow analysis. The Senior Notes are carried at amortized cost, net of deferred financing costs. The estimated fair value of the Senior Notes is based upon quoted market prices adjusted for illiquid markets. We are not aware of any factors that would significantly affect the estimated fair value subsequent to September 30, 2018 .

Partnership Equity

Partnership Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Partnership Equity	TGE Dividends to Holders of Class A Shares The following table details the dividends for the periods indicated: Three Months Ended Date Paid Dividends to Class A Shareholders Dividend per Class A Share (in thousands, except per share amounts) September 30, 2018 November 14, 2018 (1) $ 79,717 $ 0.5100 June 30, 2018 August 14, 2018 77,052 0.4975 March 31, 2018 May 15, 2018 28,316 0.4875 December 31, 2017 February 14, 2018 21,346 0.3675 September 30, 2017 November 14, 2017 20,617 0.3550 June 30, 2017 August 14, 2017 19,891 0.3425 March 31, 2017 May 15, 2017 16,697 0.2875 (1) The dividend announced on October 15, 2018 for the third quarter of 2018 will be paid on November 14, 2018 to Class A shareholders of record at the close of business on October 31, 2018 . Subsidiary Distributions TEP Distributions . The following table shows the distributions for the periods indicated: Distributions Distribution Limited Partner General Partner Three Months Ended Date Paid Incentive Distribution Rights General Partner Units Total (in thousands, except per unit amounts) March 31, 2018 May 15, 2018 $ 71,370 $ 39,816 $ 1,267 $ 112,453 $ 0.9750 December 31, 2017 February 14, 2018 70,638 39,125 1,251 111,014 0.9650 September 30, 2017 November 14, 2017 69,174 37,744 1,219 108,137 0.9450 June 30, 2017 August 14, 2017 67,671 36,342 1,186 105,199 0.9250 March 31, 2017 May 15, 2017 60,486 29,840 1,040 91,366 0.8350 As a result of the TEP Merger, Tallgrass Equity and its wholly-owned subsidiary, Tallgrass Equity Investments, LLC, will receive all distributions paid by TEP for the second quarter of 2018 and subsequent periods. Exchange Rights Our current Class B shareholders (collectively, the "Exchange Right Holders") own an equal number of Tallgrass Equity units. The Exchange Right Holders, and any permitted transferees of their Tallgrass Equity units, each have the right to exchange all or a portion of their Tallgrass Equity units for Class A shares at an exchange ratio of one Class A share for each Tallgrass Equity unit exchanged, which we refer to as the Exchange Right. The Exchange Right may be exercised only if, simultaneously therewith, an equal number of our Class B shares are transferred by the exercising party to us. Upon such exchange, we will cancel the Class B shares received from the exercising party. During the nine months ended September 30, 2018 , 2,403,766 Class A shares were issued and an equal number of Class B shares were cancelled as a result of the exercise of the Exchange Right. During the period from October 1, 2018 to October 31, 2018, 417,566 Class A shares were issued and an equal number of Class B shares were cancelled as a result of the exercise of the Exchange Right. Equity Distribution Agreements Neither TGE or TEP currently have equity distribution agreements in place. TEP was previously a party to equity distribution agreements pursuant to which it sold from time to time through a group of managers, as its sales agents, TEP common units representing limited partner interests. Following the TEP Merger, these agreements were terminated effective July 2, 2018. During the nine months ended September 30, 2018 , TEP did not issue any common units under its equity distribution agreements. During the nine months ended September 30, 2017 , TEP issued and sold 2,341,061 common units with a weighted average sales price of $48.82 per unit under its equity distribution agreements for net cash proceeds of approximately $112.4 million (net of approximately $1.9 million in commissions and professional service expenses). Repurchase of TEP Common Units Owned by TD Following an offer received from TD with respect to TEP common units owned by TD not subject to the call option, TEP repurchased 736,262 TEP common units from TD at an aggregate price of approximately $35.3 million , or $47.99 per common unit, on February 1, 2017, which was approved by the conflicts committee of the board of directors of TEP's general partner. These common units were deemed canceled upon TEP's purchase and as of such transaction date were no longer issued and outstanding. Noncontrolling Interests As of September 30, 2018 , noncontrolling interests in our subsidiaries consisted of a 44.36% interest in Tallgrass Equity held by the Exchange Right Holders and an approximate 40% membership interest in Deeprock Development. During the nine months ended September 30, 2018 , we recognized contributions from and distributions to noncontrolling interests of $0.2 million and $262.9 million , respectively. Contributions from noncontrolling interests consisted primarily of contributions from TD to Pony Express. Distributions to noncontrolling interests consisted of Tallgrass Equity distributions to the Exchange Right Holders of $160.6 million , distributions to TEP unitholders of $97.7 million , and distributions to Deeprock Development and Pony Express noncontrolling interests of $4.6 million . During the nine months ended September 30, 2017 , we recognized contributions from and distributions to noncontrolling interests of $1.1 million and $229.7 million , respectively. Contributions from noncontrolling interests consisted primarily of contributions from TD to Pony Express. Distributions to noncontrolling interests consisted of distributions to TEP unitholders of $135.4 million , Tallgrass Equity distributions to the Exchange Right Holders of $90.0 million and distributions to Pony Express noncontrolling interests of $4.3 million . Other Contributions and Distributions During the nine months ended September 30, 2018 , TGE recognized the following other contributions and distributions: • TGE was deemed to have made a noncash capital distribution of $198.0 million , which represents the excess purchase price over the $53.8 million carrying value of the 5,619,218 TEP common units acquired as of February 7, 2018; and • TGE was deemed to have received a noncash capital contribution of $108.5 million , which represents the excess carrying value of the 25.01% membership interest in Rockies Express acquired as of February 7, 2018 over the fair value of the consideration paid. During the nine months ended September 30, 2017 , TGE recognized the following other contributions and distributions: • TEP received contributions from TD of $2.3 million primarily to indemnify TEP for costs associated with Trailblazer's Pipeline Integrity Management Program, as discussed in Note 15 – Legal and Environmental Matters .

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contract with Customers	Implementation of ASC Topic 606 As discussed in Note 2 – Summary of Significant Accounting Policies , we adopted the guidance in ASC Topic 606 effective January 1, 2018 using the modified retrospective method of adoption. As a result, revenue reported for the three and nine months ended September 30, 2017 has not been revised. The following tables provide the impact of ASC Topic 606 on our condensed consolidated balance sheet as of September 30, 2018 and the condensed consolidated statements of income for the three and nine months ended September 30, 2018 : September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Unconsolidated investments $ 1,872,879 $ 1,796,606 $ 76,273 (1) Three Months Ended September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Crude oil transportation services $ 100,226 $ 100,348 $ (122 ) (2) Sales of natural gas, NGLs, and crude oil $ 44,072 $ 45,225 $ (1,153 ) (3) Processing and other revenues $ 25,069 $ 25,630 $ (561 ) (1)(3) Cost of sales $ 28,556 $ 30,248 $ (1,692 ) (2)(3) Equity in earnings of unconsolidated investments $ 76,268 $ 64,704 $ 11,564 (1) Net income attributable to TGE $ 59,550 $ 53,366 $ 6,184 Basic net income per Class A share $ 0.38 $ 0.34 $ 0.04 Diluted net income per Class A share $ 0.38 $ 0.34 $ 0.04 Nine Months Ended September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Crude oil transportation services $ 286,130 $ 286,136 $ (6 ) (2) Sales of natural gas, NGLs, and crude oil $ 119,467 $ 122,834 $ (3,367 ) (3) Processing and other revenues $ 72,783 $ 75,846 $ (3,063 ) (1)(3) Cost of sales $ 82,601 $ 88,846 $ (6,245 ) (2)(3) Equity in earnings of unconsolidated investments $ 222,857 $ 189,450 $ 33,407 (1) Net income attributable to TGE $ 77,348 $ 67,701 $ 9,647 Basic net income per Class A share $ 0.85 $ 0.74 $ 0.11 Diluted net income per Class A share $ 0.85 $ 0.74 $ 0.11 (1) Reflects the impact on our investment in Rockies Express and the management fee collected by NatGas of the cumulative effect adjustment at Rockies Express, which arose as a result of the allocation of the transaction price to a series of individual performance obligations in certain long-term transportation contracts with tiered-pricing arrangements. The adjustment increases the carrying amount of our investment in Rockies Express to reflect increased equity in earnings and establishes a receivable for the increased management fee revenue that would have been earned by NatGas. (2) Reflects the impact to revenue and cost of sales to value PLA barrels collected under certain crude oil transportation arrangements at their contract inception fair value in revenue and record an associated lower of cost or net realizable value adjustment in cost of sales. (3) Reflects the reclassification of certain gathering and processing fees collected under arrangements determined to be supply arrangements, rather than customer arrangements under ASC 606, to cost of sales and the reclassification of certain commodities retained as consideration for processing services to processing fee revenue. Disaggregated Revenue A summary of our revenue by line of business is as follows: Three Months Ended September 30, 2018 Natural Gas Transportation segment Crude Oil Transportation segment Gathering, Processing, & Terminalling segment Corporate and Other Total Revenue (in thousands) Crude oil transportation - committed shipper revenue $ — $ 100,614 $ — $ — $ 100,614 Natural gas transportation - firm service 31,070 — — (793 ) 30,277 Water business services — — 12,837 — 12,837 Natural gas gathering & processing fees — — 6,631 — 6,631 All other (1) 2,551 13,321 6,709 (17,636 ) 4,945 Total service revenue 33,621 113,935 26,177 (18,429 ) 155,304 Natural gas liquids sales — — 26,201 — 26,201 Natural gas sales 456 — 5,517 — 5,973 Crude oil sales — 2,315 147 — 2,462 Total commodity sales revenue 456 2,315 31,865 — 34,636 Total revenue from contracts with customers 34,077 116,250 58,042 (18,429 ) 189,940 Other revenue (2) — — 13,570 (3,190 ) 10,380 Total revenue (3) $ 34,077 $ 116,250 $ 71,612 $ (21,619 ) $ 200,320 Nine Months Ended September 30, 2018 Natural Gas Transportation segment Crude Oil Transportation segment Gathering, Processing, & Terminalling segment Corporate and Other Total Revenue (in thousands) Crude oil transportation - committed shipper revenue $ — $ 286,594 $ — $ — $ 286,594 Natural gas transportation - firm service 96,166 — — (4,074 ) 92,092 Water business services — — 38,246 — 38,246 Natural gas gathering & processing fees — — 17,429 — 17,429 All other (1) 8,240 26,124 18,809 (36,832 ) 16,341 Total service revenue 104,406 312,718 74,484 (40,906 ) 450,702 Natural gas liquids sales — — 77,287 — 77,287 Natural gas sales 802 — 17,907 — 18,709 Crude oil sales — 6,290 515 — 6,805 Total commodity sales revenue 802 6,290 95,709 — 102,801 Total revenue from contracts with customers 105,208 319,008 170,193 (40,906 ) 553,503 Other revenue (2) — — 28,869 (9,369 ) 19,500 Total revenue (3) $ 105,208 $ 319,008 $ 199,062 $ (50,275 ) $ 573,003 (1) Includes revenue from crude oil transportation walk up shippers, crude oil terminal services, interruptible natural gas transportation and storage, and natural gas park and loan service. (2) Includes lease and derivative revenue not subject to ASC 606. (3) Excludes $225.8 million and $683.4 million of revenue recognized at Rockies Express for the three and nine months ended September 30, 2018 , respectively. See Note 7 – Investments in Unconsolidated Affiliates for additional information about our investment in Rockies Express. Performance Obligations A performance obligation is a promise in a contract to transfer a distinct good or service to the customer, and is the unit of account in ASC Topic 606. A contract's transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. The majority of our contracts have a single performance obligation and are billed and collected monthly. All of our segments engage in commodity sales, in which our performance obligations include an obligation to deliver the specified volume of a commodity to the designated receipt point. Revenue from commodity sales is recognized at a point in time when the customer obtains control of the commodity, typically upon delivery to the designated delivery point when the customer accepts and takes possession of the commodity. In the Natural Gas Transportation segment, our performance obligations typically include an obligation to stand ready to provide natural gas transportation, storage, or an integrated transportation and storage service over the life of the contract, which is a series. These performance obligations are satisfied over time using each day of service to measure progress toward satisfaction of the performance obligation. In the Crude Oil Transportation segment, our performance obligations typically include an obligation to provide crude oil transportation services over the life of the contract, which is a series. These performance obligations are satisfied over time using barrels delivered to measure progress toward satisfaction of the performance obligation. In the Gathering, Processing & Terminalling segment, the performance obligations vary based on the operating asset and type of contract. In our natural gas gathering and processing arrangements, performance obligations typically include an obligation to provide an integrated processing service over the life of the contract, which is a series. These performance obligations are satisfied over time using each unit of gas processed to measure progress toward satisfaction of the performance obligation. In our freshwater supply arrangements, performance obligations typically include an obligation to deliver a specified volume of water to the designated receipt point. These performance obligations are satisfied at a point in time when the customer obtains control of the water. In our produced water gathering and disposal arrangements, performance obligations typically include an obligation to provide an integrated produced water gathering and disposal service over the life of the contract, which is a series. These performance obligations are satisfied over time using barrels disposed to measure progress toward satisfaction of the performance obligation. On September 30, 2018 , we had $1.5 billion of remaining performance obligations at our consolidated subsidiaries, which we refer to as total backlog. Total backlog includes performance obligations under long-term crude oil transportation contracts with committed shippers, natural gas firm transportation and firm storage contracts, and certain water business service contracts with minimum volume commitments, and excludes variable consideration that is not estimated at contract inception, as discussed further below. We expect to recognize the total backlog during the remainder of 2018 and future periods as follows (in thousands): Year Estimated Revenue 2018 $ 129,104 2019 496,227 2020 328,066 2021 148,967 2022 136,316 Thereafter 271,512 Total $ 1,510,192 Contract Estimates Accounting for long-term contracts involves the use of various techniques to estimate total contract revenue. Contract estimates are based on various assumptions to project the outcome of future events that often span several years. These assumptions include the anticipated volumes of crude oil expected to be delivered by our customers for transport in future periods. The nature of our contracts gives rise to several types of variable consideration, including PLA, volumetric charges for actual volumes delivered, overrun charges, and other fees that are contingent on the actual volumes delivered by our customers. As the amount of variable consideration is allocable to each distinct performance obligation within the series of performance obligations that comprise the single performance obligation and the uncertainty related to the consideration is resolved each month as the distinct service is provided, we do not estimate the total variable consideration for the single overall performance obligation. Consequently, we are able to include in the transaction price each month the actual amount of variable consideration because no uncertainty exists surrounding the services provided that month. Certain of our contracts include provisions in which a portion of the consideration is noncash. In our Crude Oil Transportation segment, we collect PLA from our customers. As crude oil is transported, we earn, and take title to, a portion of the oil transported for our services. Any PLA that remains after replacing losses in transit can be sold. Where PLA is determined to be a component of compensation for the transportation services provided, crude oil retained is recognized in revenue at its contract inception fair value. In our Gathering, Processing & Terminalling segment, we retain commodity products as consideration under certain of our gathering and processing arrangements. Processing fee revenue is recorded when the performance obligation is completed based on the value of the product received at the time services are performed. At this time, the variability of the non-cash consideration related to both form (price) and other-than-form (volume and product mix), which are interrelated, is resolved. As a significant change in one or more of these estimates could affect the amount and timing of revenue recognized under our customer contracts, we review and update our contract-related estimates regularly. Contract Balances The timing of revenue recognition, billings, and cash collections may result in billed accounts receivable, unbilled receivables (contract assets), and deferred revenue (contract liabilities) on our condensed consolidated balance sheets. Revenue is generally billed and collected monthly based on services provided or commodity volumes sold. In our Crude Oil Transportation segment, we recognize shipper deficiencies, or deferred revenue, for barrels committed by the customer to be transported in a month but not physically received by us for transport or delivered to the customers' agreed upon destination point. These shipper deficiencies are charged at the committed tariff rate per barrel and recorded as a contract liability until the barrels are physically transported and delivered, or when the likelihood that the customer will utilize the deficiency balance becomes remote. We also recognize contract liabilities, in the form of deferred revenue, under certain water business services contracts in the Gathering, Processing & Terminalling segment. Contract balances as of September 30, 2018 were as follows: September 30, 2018 January 1, 2018 (in thousands) Accounts receivable from contracts with customers $ 67,603 $ 61,888 Other accounts receivable 168,097 56,727 Accounts receivable, net $ 235,700 $ 118,615 Deferred revenue from contracts with customers (1) $ 103,652 $ 88,471 (1) Revenue recognized during the three and nine months ended September 30, 2018 that was included in the deferred revenue balance at the beginning of the period was $2.0 million and $9.3 million , respectively. This revenue primarily represented the utilization of shipper deficiencies at Pony Express.

Net Income per Class A Share

Net Income per Class A Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income per Class A Share	Basic net income per Class A share is determined by dividing net income attributable to TGE by the weighted average number of outstanding Class A shares during the period. Class B shares do not share in the earnings of TGE. Accordingly, basic and diluted net income per Class B share has not been presented. Diluted net income per Class A share is determined by dividing net income attributable to TGE by the weighted average number of outstanding diluted Class A shares during the period. For purposes of calculating diluted net income per Class A share, we considered the impact of possible future exercises of the Exchange Right by the Exchange Right Holders on both net income attributable to TGE and the diluted weighted average number of Class A shares outstanding. The Exchange Right Holders refers to the group of persons who collectively own all TGE's outstanding Class B shares and an equivalent number of Tallgrass Equity units. The Exchange Right Holders are entitled to exercise the right to exchange their Tallgrass Equity units (together with an equivalent number of TGE Class B shares) for TGE Class A shares at an exchange ratio of one TGE Class A share for each Tallgrass Equity unit exchanged, which we refer to as the Exchange Right. The Exchange Right Holders primarily consist of Kelso & Company and its affiliated investment funds, The Energy & Minerals Group and its affiliated investment funds, and Tallgrass KC, LLC, which is an entity owned by certain members of TGE's management. Pursuant to the TGE partnership agreement and the Tallgrass Equity limited liability company agreement, our capital structure and the capital structure of Tallgrass Equity will generally replicate one another in order to maintain the one-for-one exchange ratio between the Tallgrass Equity units and Class B shares, on the one hand, and our Class A shares, on the other hand. As a result, the exchange of any Class B shares for Class A shares does not have a dilutive effect on basic net income per Class A share. However, for the three and nine months ended September 30, 2018 and 2017 , the potential issuance of TGE Equity Participation Shares would have had a dilutive effect on basic net income per Class A share. Effective June 30, 2018 with the completion of the TEP Merger, as discussed in Note 1 – Description of Business , TEP's outstanding Equity Participation Units were converted to Equity Participation Shares at a ratio of 2.0 Equity Participation Shares for each outstanding TEP Equity Participation Unit. As of September 30, 2018, TGE has 1,968,908 outstanding Equity Participation Shares with a weighted average grant date fair value of $18.93 , and expects to recognize $19.6 million of total compensation cost related to non-vested Equity Participation Shares over a weighted average period of 2.9 years . The following table illustrates the calculation of net income per Class A share for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per unit amounts) Basic Net Income per Class A Share Net income attributable to TGE $ 59,550 $ 15,866 $ 77,348 $ 36,648 Basic weighted average Class A Shares outstanding 155,001 58,075 91,183 58,075 Basic net income per Class A share $ 0.38 $ 0.27 $ 0.85 $ 0.63 Diluted Net Income per Class A Share Net income attributable to TGE $ 59,550 $ 15,866 $ 77,348 $ 36,648 Incremental net income attributable to TGE including the effect of the assumed issuance of Equity Participation Shares 304 64 1,097 132 Net income attributable to TGE including incremental net income from assumed issuance of Equity Participation Shares $ 59,854 $ 15,930 $ 78,445 $ 36,780 Basic weighted average Class A Shares outstanding 155,001 58,075 91,183 58,075 Equity Participation Shares equivalent shares 1,087 117 1,478 118 Diluted weighted average Class A Shares outstanding 156,088 58,192 92,661 58,193 Diluted net income per Class A Share $ 0.38 $ 0.27 $ 0.85 $ 0.63

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Regulated Operations [Abstract]
Regulatory Matters	There are no regulatory proceedings challenging the rates of Pony Express, Rockies Express, or Tallgrass Interstate Gas Transmission, LLC ("TIGT"). On June 29, 2018, Trailblazer Pipeline Company LLC ("Trailblazer") filed a general rate case with the FERC pursuant to Section 4 of the Natural Gas Act ("NGA"), as further described below. We have also made certain regulatory filings with the FERC, including the following: Pony Express On May 22, 2017 and May 31, 2017, Pony Express made tariff filings with the FERC in Docket Nos. IS17-263-000, IS17-464-000, and IS17-465-000 to increase the contract and non-contract rates by an amount reflecting the FERC annual index adjustment of approximately 0.2% , which became effective July 1, 2017. On November 30, 2017, Pony Express filed with the FERC in Docket No. IS18-60-000 certain changes to its tariffs to reflect the addition of two new destination points, which became effective January 1, 2018. On December 29, 2017, Pony Express filed with the FERC in Docket No. IS18-113-000 certain changes to its tariffs to reflect a new origin point in Rooks County, Kansas, which became effective on February 1, 2018. On February 28, 2018, Pony Express filed with the FERC in Docket No. IS18-199-000 certain changes to its tariffs to reflect a new origin point in Platteville, Colorado, which became effective on April 1, 2018. On March 1, 2018, Pony Express submitted proposed revisions to its Rules and Regulations Tariff in Docket No. IS18-204-000 to establish the right to accept "Specialty Batches" of oil that do not conform to the Quality Specifications reflected in the tariff, provided that the acceptance is operationally feasible. These tariff changes became effective on April 1, 2018. On April 11, 2018, Pony Express filed with the FERC in Docket No. IS18–267–000 certain changes to its tariffs to reflect additional contract rates from a new origin point in Platteville, Colorado, which became effective May 1, 2018. On May 2, 2018, Pony Express filed with the FERC in Docket No. IS18-297-000 certain changes to its rules and regulations applicable to new intermediate off-system storage points, which became effective May 15, 2018. On May 31, 2018, Pony Express made tariff filings with the FERC in Docket No. IS18-570-000 to increase the contract and non-contract rates by an amount reflecting the FERC annual index adjustment of approximately 4.4% which became effective July 1, 2018. Rockies Express Rockies Express Zone 3 Capacity Enhancement Project – FERC Docket No. CP15-137-000 On March 31, 2015 in Docket No. CP15-137-000, Rockies Express filed with the FERC an application for authorization to construct and operate (1) three new mainline compressor stations located in Pickaway and Fayette Counties, Ohio and Decatur County, Indiana; (2) additional compressors at an existing compressor station in Muskingum County, Ohio; and (3) certain ancillary facilities. The facilities increased the Rockies Express Zone 3 east-to-west mainline capacity by 0.8 Bcf/d. Pursuant to the FERC's obligations under the National Environmental Policy Act, FERC staff issued an Environmental Assessment for the project on August 31, 2015. On February 25, 2016, the FERC issued a Certificate of Public Convenience and Necessity authorizing Rockies Express to proceed with the project. On March 14, 2016, Rockies Express commenced construction of the project facilities. The project was placed in-service for the full 0.8 Bcf/d on January 6, 2017. Electric Power Charge Clarification - FERC Docket No. RP17-285 On December 21, 2016, in Docket No. RP17-285, Rockies Express proposed certain revisions to the General Terms and Conditions of its tariff to clarify that the electric power costs associated with the operation of gas coolers installed in association with the Zone 3 Capacity Enhancement Project at both electric and gas powered stations, will be included in the Power Cost Tracker. Several shippers submitted comments on the proposal. The FERC issued an order on January 19, 2017 accepting the proposed revisions permitting the recovery of electric power costs from the operation of both gas and electric powered compressor stations, subject to certain clarifications. 2017 Annual and Interim FERC Fuel Tracking Filings - FERC Docket Nos. RP17-401 and RP17-1064 On February 13, 2017, in Docket No. RP17-401, Rockies Express made its annual fuel and power cost tracker filing with a proposed effective date of April 1, 2017. The FERC issued an order accepting the filing, including certain requested waivers, on March 21, 2017. On September 20, 2017, Rockies Express made its interim fuel tracker filing in Docket No. RP17-1064 with a proposed effective date of November 1, 2017. The FERC issued an order accepting the filing on October 18, 2017. Increased Frequency of FL&U and PCT Adjustments - FERC Docket No. RP18-228 On December 1, 2017, in Docket No. RP18-228, Rockies Express made a filing with the FERC to increase the frequency in which it may adjust fixed fuel and lost and unaccounted for retainages and power cost tracker charges during the year so that its recovery of fixed fuel and lost and unaccounted for charges and power costs more closely track usage. Rockies Express proposed an effective date of April 1, 2018. The comment period ended on December 13, 2017, and no parties opposed Rockies Express' filing. On April 4, 2018, the FERC issued a letter order accepting Rockies Express' proposal, subject to certain modifications. Rockies Express submitted a compliance filing reflecting the approved tariff provisions and requested modifications on April 10, 2018. No comments on the compliance filing were submitted by the comment deadline of April 16, 2018. On April 18, 2018, the FERC issued an order accepting Rockies Express' compliance filing effective April 19, 2018. 2018 Annual FERC Fuel Tracking Filing - FERC Docket No. RP18-453 On February 20, 2018, in Docket No. RP18-453, Rockies Express made its annual fuel and power cost tracker filing with a proposed effective date of April 1, 2018. The FERC issued an order accepting the filing on March 19, 2018. Cheyenne Hub Enhancement Project - FERC Docket CP18-103 On March 2, 2018, Rockies Express submitted an application pursuant to section 7(c) of the NGA for a certificate of public convenience and necessity authorizing the construction and operation of certain booster compressor units and ancillary facilities located at the Cheyenne Hub in Weld County, Colorado that will enable Rockies Express to provide a new hub service allowing for firm receipts and deliveries between Rockies Express and certain other interconnected pipelines at the Cheyenne Hub. Rockies Express filed this certificate application in conjunction with a concurrently filed certificate application by Cheyenne Connector, LLC ("Cheyenne Connector") for the Cheyenne Connector Pipeline Project further described below. The comment period for the Cheyenne Hub Enhancement Project closed on April 9, 2018. To date, various comments have been filed by market participants and others regarding the proposed project. Rockies Express has also responded to data requests from FERC's relevant program offices. On October 11, 2018, FERC issued a Notice of Schedule of Environmental Review setting December 18, 2018 as the date of issuance of the Environmental Assessment and March 18, 2019 as the deadline for decisions by other federal agencies on requests for authorizations for the proposed project. Cheyenne Connector Cheyenne Connector Pipeline Project - FERC Docket CP18-102 On March 2, 2018, Cheyenne Connector, an indirect subsidiary of TGE, submitted an application pursuant to section 7(c) of the NGA for a certificate of public convenience and necessity to construct and operate a 70 -mile 36 inch pipeline to transport natural gas from multiple gas processing plants in Weld County, Colorado to Rockies Express' Cheyenne Hub. The comment period for the Cheyenne Connector Pipeline Project closed on April 9, 2018. To date, various comments have been filed by market participants and others regarding the proposed project. Cheyenne Connector has also responded to data requests from FERC's relevant program offices. On October 11, 2018, FERC issued a Notice of Schedule of Environmental Review setting December 18, 2018 as the date of issuance of the Environmental Assessment and March 18, 2019 as the deadline for decisions by other federal agencies on requests for authorizations for the proposed project. TIGT General Rate Case Filing - FERC Docket No. RP16-137-000, et seq. On October 30, 2015, in Docket No. RP16-137-000, et seq. , TIGT filed a general rate case with the FERC pursuant to Section 4 of the NGA. The general rate case was ultimately resolved via settlement, which the FERC approved on November 2, 2016, and a compliance filing that modernized TIGT's FERC Gas Tariff, consistent with prior FERC orders, which the FERC accepted on March 16, 2017. Per the terms of the settlement, TIGT is required to file a new general rate case on May 1, 2019 (provided that such rate case is not pre-empted by a pre-filing settlement). 2017 Annual Fuel Tracker Filing - FERC Docket No. RP17-428-000 On February 27, 2017, in Docket No. RP17-428-000, TIGT made its annual fuel tracker filing with a proposed effective date of April 1, 2017. The filing incorporated the FL&U tracker and power cost tracker mechanisms agreed to in the TIGT Rate Case Settlement. The FERC accepted the filing on March 21, 2017. Electric Power Charge Clarification - FERC Docket No. RP17-1051-000 On September 15, 2017, in Docket No. RP17-1051-000, TIGT proposed certain revisions to its tariff to clarify, amongst other things, that the electric power costs associated with the operation of gas coolers at both electric and gas powered stations are properly included in the Power Cost Tracker. The FERC issued an order on October 3, 2017 accepting the proposed revisions. 2018 Annual Fuel Tracker Filing - FERC Docket No. RP18-533-000 On March 1, 2018, in Docket No. RP18-533-000, TIGT made its annual fuel tracker filing with a proposed effective date of April 1, 2018. The FERC accepted the filing on March 22, 2018. Trailblazer 2017 Annual and Interim Fuel Tracker Filings - FERC Docket Nos. RP17-549-000 and RP17-1052-000 On March 22, 2017, in Docket No. RP17-549-000, Trailblazer made its annual fuel tracker filing with a proposed effective date of May 1, 2017. The FERC accepted the filing on April 19, 2017. On September 15, 2017, Trailblazer made its interim fuel tracker filing in Docket No. RP17-1052-000 with a proposed effective date of November 1, 2017. The FERC accepted the filing on October 13, 2017. 2018 Annual Fuel Tracker Filing - FERC Docket No. RP18-580-000 On March 22, 2018, in Docket No. in Docket No. RP18-580-000, Trailblazer made its annual fuel tracker filing with a proposed effective date of May 1, 2018. The FERC accepted the filing on April 20, 2018. General Rate Case Filing - FERC Docket No. RP18-922-000, et seq. On June 29, 2018, Trailblazer filed a general rate case with the FERC, which satisfies the requirement set forth in the settlement resolving Trailblazer's previous general rate case that Trailblazer file a new general rate case with rates to be effective no later than January 1, 2019. The June 29, 2018 filing reflects an overall increase to Trailblazer's cost of service. In the filing, Trailblazer is proposing to maintain its existing bifurcated firm transportation service rate design as well as its current tracking methodologies for the treatment of Fuel and Lost and Unaccounted For ("FL&U") gas and electric power costs. The proposed rates include an increase in rates on Trailblazer's Existing System Firm Transportation Service. The overall rate increase would be partially offset by a proposed decrease in rates for Expansion System Firm Transportation Service and interruptible services. Trailblazer is also proposing to include a cost recovery mechanism in its tariff to recover future eligible costs related to system safety, integrity, reliability, environmental and cybersecurity issues. Under the NGA and the FERC's regulations, Trailblazer's shippers and other interested parties, including the FERC's Trial Staff, have the right to challenge any aspect of Trailblazer's rate case filing. On July 11, 2018, four protests were filed that challenge various aspects of Trailblazer's rate case filing. FERC action remains pending. On July 31, 2018, the FERC issued an Order accepting and suspending the rate case filing, and establishing hearing and settlement procedures. In the Order, the FERC approved the as-filed rate decreases for Expansion System Firm Transportation Service, as well as Trailblazer’s interruptible services, effective August 1, 2018. The Commission also established a paper hearing to examine the extent to which Trailblazer is entitled to an Income Tax Allowance. All remaining issues, including the proposed rate increases to Existing System Firm Transportation Service have been set for hearing and are accepted effective January 1, 2019, subject to refund. On August 30, 2018, Trailblazer and certain of Trailblazer's shippers filed a request for rehearing of the July 31, 2018 Order, which remains pending before the FERC. Consistent with the July 31, 2018 Order, on August 30, 2018, certain of Trailblazer's shippers and other interested parties filed initial briefs regarding the Income Tax Allowance issue. Trailblazer filed its reply brief regarding the same on September 14, 2018. The briefs remain pending before the FERC. On August 28, 2018, the participants attended an initial settlement conference. On September 12, 2018, the Chief Administrative Law Judge issued an order continuing settlement judge procedures. The second settlement conference is scheduled for November 15, 2018.

Legal and Environmental Matters

Legal and Environmental Matters	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Legal and Environmental Matters	Legal In addition to the matters discussed below, we are a defendant in various lawsuits arising from the day-to-day operations of our business. Although no assurance can be given, we believe, based on our experiences to date, that the ultimate resolution of such matters will not have a material adverse impact on our business, financial position, results of operations, or cash flows. We have evaluated claims in accordance with the accounting guidance for contingencies that we deem both probable and reasonably estimable and, accordingly, have recorded no reserve for legal claims as of September 30, 2018 or December 31, 2017 . Rockies Express Ultra Resources In early 2016, Ultra Resources, Inc. ("Ultra") defaulted on its firm transportation service agreement for approximately 0.2 Bcf/d through November 11, 2019. In late March 2016, Rockies Express terminated Ultra's service agreement. On April 14, 2016, Rockies Express filed a lawsuit against Ultra for breach of contract and damages in Harris County, Texas, seeking approximately $303 million in damages and other relief. On April 29, 2016, Ultra and certain of its debtor affiliates filed for protection under Chapter 11 of the United States Bankruptcy Code in United States Bankruptcy Court for the Southern District of Texas, which operated as a stay of the Harris County state court proceeding. On January 12, 2017, Rockies Express and Ultra entered into an agreement to settle Rockies Express' approximately $303 million claim against Ultra. In accordance with the settlement agreement, Ultra made a cash payment to Rockies Express of $150 million on July 12, 2017, and entered into a new, seven-year firm transportation agreement with Rockies Express commencing December 1, 2019, for west-to-east service of 0.2 Bcf/d at a rate of approximately $0.37 per dth/d, or approximately $26.8 million annually. TEP received its proportionate distribution from the cash settlement payment in July 2017. Environmental, Health and Safety We are subject to a variety of federal, state and local laws that regulate permitted activities relating to air and water quality, waste disposal, and other environmental matters. We currently believe that compliance with these laws will not have a material adverse impact on our business, cash flows, financial position or results of operations. However, there can be no assurances that future events, such as changes in existing laws, the promulgation of new laws, or the development of new facts or conditions will not cause us to incur significant costs. We had environmental reserves of $7.5 million and $7.7 million at September 30, 2018 and December 31, 2017 , respectively. Rockies Express Seneca Lateral On January 31, 2018, Rockies Express experienced an operational disruption on its Seneca Lateral due to a pipe rupture and natural gas release in a rural area in Noble County, Ohio. There were no injuries reported and no evacuations. The release required Rockies Express to shut off the flow through the segment until February 27, 2018, when temporary repairs were completed allowing the segment to be placed back into service. Total cost of remediation is expected to be approximately $6.1 million prior to any insurance recoveries. Rockies Express expects to recover a significant majority of these costs from insurance. Permanent repairs were completed in September 2018. TMID Casper Plant, EPA Notice of Violation In August 2011, the EPA and the Wyoming Department of Environmental Quality ("WDEQ") conducted an inspection of the Leak Detection and Repair ("LDAR") Program at the Casper Gas Plant in Wyoming. In September 2011, Tallgrass Midstream, LLC ("TMID") received a letter from the EPA alleging violations of the Standards of Performance of Equipment Leaks for Onshore Natural Gas Processing Plant requirements under the Clean Air Act. TMID received a letter from the EPA concerning settlement of this matter in April 2013 and received additional settlement communications from the EPA and Department of Justice beginning in July 2014. Settlement negotiations are continuing, including the expected inclusion of TIGT as a party to any possible settlement as a result of TIGT owning a compressor that is located adjacent to the Casper Gas Plant site. Casper Gas Plant On November 25, 2014, WDEQ issued a Notice of Violation for violations of Part 60 Subpart OOOO related to the Depropanizer project (wv-14388, issued 7/9/13) in Docket No. 5506-14. TMID had discussed the issues in a meeting with WDEQ in Cheyenne on November 17, 2014, and submitted a disclosure on November 20, 2014 detailing the regulatory issues and potential violations. The project triggered a modification of Subpart OOOO for the entire plant. The project equipment as well as plant equipment subjected to Subpart OOOO was not monitored timely, and initial notification was not made timely. Settlement negotiations with WDEQ are currently ongoing. TMG Archibald Booster Station Tallgrass Midstream Gathering, LLC ("TMG") is currently a party to a remedy agreement entered into with the WDEQ in July 2013 with respect to the Archibald Booster Station located in Campbell County, Wyoming. In connection with the remedy agreement, TMG has agreed to complete certain remedial actions at the site related to a former earthen pit including semi-annual groundwater sampling, and quarterly recovery activities at monitoring wells. The facility is currently in compliance with the WDEQ under the remedy agreement. Irwin Booster Station TMG is also party to a remedy agreement entered into with the WDEQ in July 2013 with respect to the Irwin Booster Station located in Converse County, Wyoming. In connection with the remedy agreement, TMG has agreed to complete certain remedial actions at the site related to a former earthen pit including semi-annual groundwater sampling. The facility is currently in compliance with the WDEQ under the remedy agreement. Trailblazer Pipeline Integrity Management Program Starting in 2014 Trailblazer's operating capacity was decreased as a result of smart tool surveys that identified approximately 25 - 35 miles of pipe as potentially requiring repair or replacement. During 2016 and 2017, Trailblazer incurred approximately $21.8 million of remediation costs to address this issue, including replacing approximately 8 miles of pipe. To date the pressure and capacity reduction has not prevented Trailblazer from fulfilling its firm service obligations at existing subscription levels or had a material adverse financial impact on us. However, Trailblazer continued performing remediation to increase and maximize its operating capacity over the long-term and expects to spend in excess of $20 million during 2018 for this pipe replacement and remediation work. As of October 2018, the pipeline was returned to its maximum allowable operating capacity. Trailblazer is exploring all possible cost recovery options to recover expenditures, including recovery through a general rate increase, negotiated rate agreements with its customers, or other FERC-approved recovery mechanisms. In connection with TEP's acquisition of Trailblazer in April 2014, TD agreed to indemnify TEP for certain out of pocket costs related to repairing or remediating the Trailblazer Pipeline. The contractual indemnity was capped at $20 million and subject to a $1.5 million deductible. TEP received the entirety of the $20 million from TD pursuant to the contractual indemnity as of December 31, 2017. Pony Express Pipeline Integrity In connection with certain crack tool runs on the Pony Express System completed in 2015, 2016, and 2017, Pony Express completed approximately $18 million of remediation for anomalies identified on the Pony Express System associated with the initial conversion and commissioning of portions of the pipeline converted from natural gas to crude oil service. Remediation work was substantially complete as of March 31, 2018.

Reporting Segments

Reporting Segments	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Reporting Segments	Our operations are located in the United States. We are organized into three reportable segments: (1) Natural Gas Transportation, (2) Crude Oil Transportation, and (3) Gathering, Processing & Terminalling. Corporate and Other includes corporate overhead costs that are not directly associated with the operations of our reportable segments, such as interest and fees associated with our revolving credit facility and the Senior Notes, public company costs, and equity-based compensation expense. Natural Gas Transportation. The Natural Gas Transportation segment is engaged in the ownership and operation of FERC-regulated interstate natural gas pipelines and an integrated natural gas storage facility that provide services to on-system customers (such as third-party LDCs), industrial users and other shippers. The Natural Gas Transportation segment includes our aggregate 75% membership interest in Rockies Express, inclusive of the additional 25.01% membership interest acquired effective February 7, 2018 . Crude Oil Transportation. The Crude Oil Transportation segment is engaged in the ownership and operation of the Pony Express System, which is a FERC-regulated crude oil pipeline serving the Bakken Shale, Denver-Julesburg and Powder River Basins, and other nearby oil producing basins. Gathering, Processing & Terminalling. The Gathering, Processing & Terminalling segment is engaged in the ownership and operation of natural gas gathering and processing facilities that produce NGLs and residue gas sold in local wholesale markets or delivered into pipelines for transportation to additional end markets; our crude oil terminal services; water business services provided primarily to the oil and gas exploration and production industry; the transportation of NGLs; and Stanchion. These segments are monitored separately by management for performance and are consistent with internal financial reporting. These segments have been identified based on the differing products and services, regulatory environment and the expertise required for their respective operations. During the second quarter of 2018, upon completion of the TEP Merger, management updated TGE's internal reporting. Beginning in the second quarter of 2018, we consider Adjusted EBITDA, as described below, to be our primary segment performance measure. We consider Adjusted EBITDA to be our primary segment performance measure as we believe it is the most meaningful measure to assess our financial condition and results of operations as a public entity. We define Adjusted EBITDA as net income excluding the impact of interest, income taxes, depreciation and amortization, non-cash income or loss related to derivative instruments, non-cash long-term compensation expense, impairment losses, gains or losses on asset or business disposals or acquisitions, gains or losses on the repurchase, redemption or early retirement of debt, and earnings from unconsolidated investments, but including the impact of distributions from unconsolidated investments and deficiency payments received from or utilized by our customers. Adjusted EBITDA is calculated and presented at the Tallgrass Equity level, before consideration of noncontrolling interest associated with the Exchange Right Holders, which we believe provides investors the most complete picture of our overall financial and operational results. The following tables set forth our segment information for the periods indicated: Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Revenue: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 34,077 $ (816 ) $ 33,261 $ 36,084 $ (1,883 ) $ 34,201 Crude Oil Transportation 116,250 (13,579 ) 102,671 93,029 (6,947 ) 86,082 Gathering, Processing & Terminalling 71,612 (7,224 ) 64,388 57,736 (2,150 ) 55,586 Total revenue $ 221,939 $ (21,619 ) $ 200,320 $ 186,849 $ (10,980 ) $ 175,869 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Revenue: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 105,208 $ (4,136 ) $ 101,072 $ 105,622 $ (4,770 ) $ 100,852 Crude Oil Transportation 319,008 (26,323 ) 292,685 273,768 (6,947 ) 266,821 Gathering, Processing & Terminalling 199,062 (19,816 ) 179,246 121,415 (7,956 ) 113,459 Total revenue $ 623,278 $ (50,275 ) $ 573,003 $ 500,805 $ (19,673 ) $ 481,132 Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Tallgrass Equity Adjusted EBITDA: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 121,433 $ (1,460 ) $ 119,973 $ 68,665 $ (530 ) $ 68,135 Crude Oil Transportation 87,567 (5,008 ) 82,559 37,425 (124 ) 37,301 Gathering, Processing & Terminalling 13,679 6,468 20,147 (1,387 ) 654 (733 ) Corporate and Other (2,317 ) — (2,317 ) (9,890 ) — (9,890 ) Reconciliation to Net Income: Add: Equity in earnings of unconsolidated investments (1) 76,268 34,841 Non-cash gain (loss) related to derivative instruments (1) 2,993 (194 ) Gain on disposal of assets (1) 279 — Gain on remeasurement of unconsolidated investment (1) — 2,744 Less: Interest expense, net (1) (34,019 ) (7,966 ) Depreciation and amortization expense (1) (27,356 ) (6,611 ) Distributions from unconsolidated investments (1) (100,720 ) (39,118 ) Non-cash compensation expense (1) (2,767 ) (664 ) Deficiency payments, net (1) (3,468 ) (645 ) Loss on debt retirement (2,245 ) Deferred income tax expense (11,997 ) (12,642 ) Net income attributable to Exchange Right Holders (57,780 ) (48,692 ) Net income attributable to TGE $ 59,550 $ 15,866 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Tallgrass Equity Adjusted EBITDA: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 253,169 $ (2,940 ) $ 250,229 $ 133,536 $ (1,349 ) $ 132,187 Crude Oil Transportation 150,943 (3,857 ) 147,086 105,784 2,286 108,070 Gathering, Processing & Terminalling 30,002 6,797 36,799 10,447 (937 ) 9,510 Corporate and Other (20,819 ) — (20,819 ) (25,631 ) — (25,631 ) Reconciliation to Net Income: Add: Equity in earnings of unconsolidated investments (1) 153,235 52,853 Gain on disposal of assets (1) 3,388 376 Non-cash gain related to derivative instruments (1) 3,306 470 Gain on remeasurement of unconsolidated investment (1) — 2,744 Less: Interest expense, net (1) (57,208 ) (20,476 ) Depreciation and amortization expense (1) (45,794 ) (19,218 ) Distributions from unconsolidated investments (1) (198,019 ) (64,848 ) Non-cash compensation expense (1) (4,738 ) (1,614 ) Deficiency payments, net (1) (7,205 ) (7,548 ) Loss on debt retirement (2,245 ) Deferred income tax expense (35,498 ) (24,982 ) Net income attributable to Exchange Right Holders (145,169 ) (105,245 ) Net income attributable to TGE $ 77,348 $ 36,648 (1) Net of noncontrolling interest associated with less than wholly-owned subsidiaries of Tallgrass Equity. Nine Months Ended September 30, Capital Expenditures: 2018 2017 (in thousands) Natural Gas Transportation $ 96,290 $ 9,829 Crude Oil Transportation 39,847 28,785 Gathering, Processing & Terminalling 125,866 49,436 Corporate and Other 3,070 — Total capital expenditures $ 265,073 $ 88,050 Assets: September 30, 2018 December 31, 2017 (in thousands) Natural Gas Transportation $ 2,602,761 $ 1,606,666 Crude Oil Transportation 1,417,853 1,407,758 Gathering, Processing & Terminalling 1,316,487 943,340 Corporate and Other 332,939 334,249 Total assets $ 5,670,040 $ 4,292,013

Subsequent Events (Notes)

Subsequent Events (Notes)	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	[PLACEHOLDER]

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These condensed consolidated financial statements and related notes for the three and nine months ended September 30, 2018 and 2017 were prepared in accordance with the accounting principles contained in the Financial Accounting Standards Board's Accounting Standards Codification, the single source of accounting principles generally accepted in the United States of America ("GAAP") for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. The year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by GAAP for annual periods. The condensed consolidated financial statements for the three and nine months ended September 30, 2018 and 2017 include all normal, recurring adjustments and disclosures that we believe are necessary for a fair statement of the results for the interim periods. In this report, the Financial Accounting Standards Board is referred to as the FASB and the FASB Accounting Standards Codification is referred to as the Codification or ASC. Certain prior period amounts have been reclassified to conform to the current presentation. Our financial results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the full year ending December 31, 2018 . The accompanying condensed consolidated interim financial statements should be read in conjunction with our audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2017 ("2017 Form 10-K") filed with the SEC on February 13, 2018.
Consolidation	The condensed consolidated financial statements include the accounts of TGE and its subsidiaries and controlled affiliates. Significant intra-entity items have been eliminated in the presentation. Net income or loss from consolidated subsidiaries that are not wholly-owned by TGE is attributed to TGE and noncontrolling interests in accordance with the respective ownership interests. A variable interest entity ("VIE") is a legal entity that possesses any of the following characteristics: an insufficient amount of equity at risk to finance its activities, equity owners who do not have the power to direct the significant activities of the entity (or have voting rights that are disproportionate to their ownership interest), or equity owners who do not have the obligation to absorb expected losses or the right to receive the expected residual returns of the entity. Companies are required to consolidate a VIE if they are its primary beneficiary, which is the enterprise that has a variable interest that could be significant to the VIE and the power to direct the activities that most significantly impact the entity's economic performance. We have presented separately in our condensed consolidated balance sheets, to the extent material, the liabilities of our consolidated VIEs for which creditors do not have recourse to our general credit. Our consolidated VIEs did not have material assets that could only be used to settle specific obligations of the consolidated VIEs. Prior to June 29, 2018, both Tallgrass Equity and TEP were considered to be VIEs under the applicable authoritative guidance and included in our consolidated results. As a result of the TEP Merger, and changes in ownership and their respective partnership arrangements, Tallgrass Equity and TEP are no longer considered to be VIEs. We continue to consolidate our membership interests in Tallgrass Equity and TEP through the voting interest model.
Use of Estimates	Use of Estimates Certain amounts included in or affecting these condensed consolidated financial statements and related disclosures must be estimated, requiring management to make certain assumptions with respect to values or conditions which cannot be known with certainty at the time the financial statements are prepared. These estimates and assumptions affect the amounts reported for assets, liabilities, revenues, and expenses during the reporting period, and the disclosure of contingent assets and liabilities at the date of the financial statements. Management evaluates these estimates on an ongoing basis, utilizing historical experience, consultation with experts and other methods it considers reasonable in the particular circumstances. Nevertheless, actual results may differ significantly from these estimates. Any effects on our business, financial position or results of operations resulting from revisions to these estimates are recorded in the period in which the facts that give rise to the revision become known.
Revenue Recognition, Policy	Revenue Recognition In May 2014, the FASB issued Accounting Standards Update ("ASU") No. 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 provides a comprehensive and converged set of principles-based revenue recognition guidelines which supersede the existing industry and transaction-specific standards. The core principle of the new guidance is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve this core principle, entities must apply a five-step process to (1) identify the contract with a customer; (2) identify the performance obligations in the contract; (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract; and (5) recognize revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 also mandates disclosure of sufficient information to enable users of financial statements to understand the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. The disclosure requirements include qualitative and quantitative information about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. Management completed its evaluation and implemented the revised guidance using the modified retrospective method as of January 1, 2018. This approach allows us to apply the new standard to (i) all new contracts entered into after January 1, 2018 and (ii) all existing contracts for which all (or substantially all) of the revenue has not been recognized under legacy revenue guidance as of January 1, 2018 through a cumulative adjustment to members' equity. Consolidated revenues presented in the comparative consolidated financial statements for periods prior to January 1, 2018 have not been revised. On January 1, 2018, we recorded a cumulative effect adjustment to equity of $44.1 million , increased the carrying amount of our investment in Rockies Express by $42.8 million , and recognized a receivable from Rockies Express of $1.3 million . These adjustments relate to the cumulative effect adjustment recorded by Rockies Express of $125.2 million upon adoption of ASC 606. The cumulative effect adjustment at Rockies Express arose as a result of the allocation of the transaction price to a series of individual performance obligations in certain long-term transportation contracts with tiered-pricing arrangements. The adjustment increases the carrying amount of our investment in Rockies Express to reflect increased equity in earnings and establishes a receivable for the increased management fee revenue that would have been earned by NatGas during the periods prior to implementation. Through our review process, we also identified the following changes to our revenue recognition policies that did not result in a cumulative effect adjustment on January 1, 2018: • Gathering & Processing. We have determined that a number of our gathering & processing contracts at TMID do not represent customer arrangements under ASC 606. Instead, arrangements deemed to represent wellhead purchases of raw gas will be accounted for as supply arrangements pursuant to ASC 705. As a result, gathering & processing fees previously recognized in revenue will be reported as a reduction to cost of sales under ASC 606. • Pipeline Loss Allowance. We have determined that pipeline loss allowance, or PLA, collected under certain crude oil transportation arrangements is a component of the transaction price where the PLA both significantly exceeds actual losses and was negotiated with the intent of providing a revenue stream to Pony Express. Under ASC 606, PLA barrels retained from customers will be subject to the guidance for noncash consideration and recognized in revenue at their contract inception fair value. See Note 12 – Revenue from Contracts with Customers for revenue disclosures related to both the implementation and the additional requirements prescribed by the standard. These new disclosures include information regarding the significant judgments used in evaluating when and how revenue is (or will be) recognized and data related to contract assets and liabilities.
Accounting Pronouncements	ASU No. 2016-02, "Leases (Topic 842)" In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). ASU 2016-02 provides a comprehensive update to the lease accounting topic in the Codification intended to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The amendments in ASU 2016-02 include a revised definition of a lease as well as certain scope exceptions. The changes primarily impact lessee accounting, while lessor accounting is largely unchanged from previous GAAP. Management is currently evaluating the impact of our pending adoption of ASC 842. The status of our implementation is as follows: • Management has formed an implementation team that meets to discuss implementation challenges, technical interpretations, industry-specific treatment of certain contract types, and project status. • Management is in the process of gathering data and reviewing contracts in order to identify all impacted contracts. • Management is evaluating the potential information technology and internal control changes that will be required for adoption based on the findings from its contract review process. • Management plans to provide internal training and awareness related to the revised guidance to the key stakeholders throughout its organization. The amendments in ASU 2016-02 are effective for public entities for annual reporting periods beginning after December 15, 2018, and for interim periods within that reporting period. Early application is permitted. We plan to adopt ASU 2016-02 on January 1, 2019 using the modified retrospective method. ASC 842 provides for a number of practical expedients. We intend to elect the following practical expedients upon adoption of ASC 842: • An entity need not reassess whether any expired or existing contracts are or contain leases. • An entity need not reassess the lease classification for any expired or existing leases. • An entity need not reassess initial direct costs for any existing leases. • An entity may elect to not assess whether existing or expired land easements that were not previously accounted for as leases are or contain a lease under ASC 842. While we are still in the process of quantifying the impact of adoption, we do not currently expect the adoption to have a material impact. We expect to recognize a right of use asset and lease liability at the implementation date, but we cannot reasonably estimate the full impact of the standard at this time. Additionally, we are currently evaluating our business processes, systems, and controls to ensure the accuracy and timeliness of the recognition and disclosure requirements under the new lease guidance.

Acquisitions & Dispositions - E

Acquisitions & Dispositions - Equity Method Investments (Policies)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments, Policy	As the aggregate 75% membership interest does not represent a controlling interest in Rockies Express, TGE's investment in Rockies Express is recorded under the equity method of accounting and is reported as "Unconsolidated investments" on our condensed consolidated balance sheets. As a result of the common control nature of the transaction, the 25.01% membership interest in Rockies Express was transferred to Tallgrass Equity at TD's historical carrying amount, including the remaining unamortized basis difference driven by the difference between the fair value of the investment and the book value of the underlying assets and liabilities on November 13, 2012, the date of acquisition by TD.

Goodwill (Policies)

Goodwill (Policies)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets, Goodwill, Policy	We evaluate goodwill for impairment on an annual basis and whenever events or changes in circumstances necessitate an evaluation for impairment. Examples of such facts and circumstances include changes in the magnitude of the excess of fair value over carrying amount in the last valuation or changes in the business environment. Our annual impairment testing date is August 31. We evaluate goodwill for impairment at the reporting unit level, which is the same as, or one level below, an operating segment as defined in the segment reporting guidance of the Codification, using either the qualitative assessment option or proceeding directly to the quantitative impairment test depending on facts and circumstances of the reporting unit. For the purpose of goodwill impairment testing, goodwill was allocated to our reporting units based on the enterprise value of each reporting unit at the date of acquisition. If we, after performing the qualitative assessment, determine it is "more likely than not" that the fair value of a reporting unit is greater than its carrying amount, then goodwill is not considered impaired. When goodwill is evaluated for impairment using the quantitative impairment test, the carrying amount of the reporting unit is compared to its fair value. If the fair value exceeds the carrying amount, goodwill is not considered impaired. If the carrying amount exceeds the reporting unit's fair value, then the reporting unit should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit.

Acquisitions & Dispositions - B

Acquisitions & Dispositions - Business Combinations (Tables)	9 Months Ended
	Sep. 30, 2018
Business Combinations [Abstract]
Equity Method Investments	At September 30, 2018 , the basis difference for our membership interests in Rockies Express was allocated as follows: Basis Difference Amortization Period (in thousands) Long-term debt $ 48,019 2 - 25 years Property, plant and equipment (1,156,562 ) 35 years Total basis difference $ (1,108,543 ) Summarized financial information for Rockies Express is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Revenue $ 225,753 $ 216,756 $ 683,426 $ 625,243 Operating income $ 127,119 $ 123,965 $ 385,831 $ 344,037 Net income to Members $ 90,707 $ 233,990 $ 270,338 $ 371,185
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed	The following represents the fair value of assets acquired and liabilities assumed (in thousands): Accounts receivable $ 2,457 Inventory 67 Property, plant and equipment 48,900 Intangible asset 46,800 (1) Accounts payable and accrued liabilities (3,224 ) Net identifiable assets acquired (excluding cash) $ 95,000 (1) The $46.8 million intangible asset acquired represents three major customer relationships. This intangible asset is amortized on a straight-line basis over a period of 8 - 14 years, the remaining terms of the underlying contracts at the time of acquisition.
Business Acquisition, Pro Forma Information	Unaudited pro forma revenue and net income attributable to TGE for the nine months ended September 30, 2018 and 2017 is presented below as if the acquisition of BNN North Dakota had been completed on January 1, 2017. Nine Months Ended September 30, 2018 2017 (in thousands) Revenue $ 573,431 $ 488,076 Net income attributable to TGE $ 77,374 $ 36,384

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Schedule of Transactions with Affiliated Companies	Totals of transactions with affiliated companies, excluding transactions disclosed elsewhere in these notes, are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Processing and other revenues (1) $ 1,838 $ 3,338 $ 5,603 $ 6,662 Cost of transportation services (2) $ — $ 1,062 $ — $ 10,476 Charges to TGE: (3) Property, plant and equipment, net $ — $ 765 $ — $ 1,568 Operations and maintenance $ — $ 7,973 $ — $ 21,680 General and administrative $ — $ 11,960 $ — $ 32,628 (1) Reflects the fee that NatGas receives as the operator of the Rockies Express Pipeline. (2) Reflects rent expense for the crude oil storage at the Deeprock Terminal prior to our consolidation of Deeprock Development during the third quarter of 2017 . (3) Charges to TGE, inclusive of Tallgrass Equity and TEP, include indirectly charged wages and salaries, other compensation and benefits, and shared services for periods prior to January 1, 2018. Effective January 1, 2018, these costs are incurred by TEP directly and, in the case of certain employee compensation and benefits, paid on TEP's behalf by its affiliate, Tallgrass Management, LLC, pursuant to the TEP Omnibus Agreement.
Schedule of Balances with Affiliates Included in Consolidated Balance Sheets	Details of balances with affiliates included in "Receivable from related parties" and "Accounts payable to related parties" in the condensed consolidated balance sheets are as follows: September 30, 2018 December 31, 2017 (in thousands) Receivable from related parties: Rockies Express Pipeline LLC $ 3,152 $ 1,340 Iron Horse Pipeline, LLC 112 — Pawnee Terminal, LLC 105 — Total receivable from related parties $ 3,369 $ 1,340 Accounts payable to related parties: Tallgrass Operations, LLC (1) $ — $ 5,342 Total accounts payable to related parties $ — $ 5,342 (1) Reflects accounts payable for charges to TGE, inclusive of Tallgrass Equity and TEP, including indirectly charged wages and salaries, other compensation and benefits, and shared services prior to January 1, 2018 as discussed above.
Schedule of Balances of Gas Imbalance with Affiliated Shippers	Gas imbalances with affiliated shippers are as follows: September 30, 2018 December 31, 2017 (in thousands) Affiliate gas imbalance receivables $ 17 $ 18 Affiliate gas imbalance payables $ 689 $ 442

Inventory - (Tables)

Inventory - (Tables)	9 Months Ended
	Sep. 30, 2018
Inventory Disclosure [Abstract]
Schedule of Components of Inventory	The components of inventory at September 30, 2018 and December 31, 2017 consisted of the following: September 30, 2018 December 31, 2017 (in thousands) Crude oil $ 18,893 $ 12,792 Materials and supplies 6,359 5,891 Natural gas liquids 364 942 Gas in underground storage 3,701 1,984 Total inventory $ 29,317 $ 21,609

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Components of Property Plant and Equipment	A summary of net property, plant and equipment by classification is as follows: September 30, 2018 December 31, 2017 (in thousands) Crude oil pipelines $ 1,290,868 $ 1,220,379 Gathering, processing and terminalling assets (1) 791,766 675,092 Natural gas pipelines 612,729 581,400 General and other 125,261 98,680 Construction work in progress 198,356 97,978 Accumulated depreciation and amortization (356,925 ) (279,192 ) Total property, plant and equipment, net $ 2,662,055 $ 2,394,337 (1) Includes approximately $46.2 million and $40.1 million of assets associated with the acquisitions of Deeprock North and BNN North Dakota, respectively, in January 2018.

Investments in Unconsolidated_2

Investments in Unconsolidated Affiliates - (Tables)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	At September 30, 2018 , the basis difference for our membership interests in Rockies Express was allocated as follows: Basis Difference Amortization Period (in thousands) Long-term debt $ 48,019 2 - 25 years Property, plant and equipment (1,156,562 ) 35 years Total basis difference $ (1,108,543 ) Summarized financial information for Rockies Express is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Revenue $ 225,753 $ 216,756 $ 683,426 $ 625,243 Operating income $ 127,119 $ 123,965 $ 385,831 $ 344,037 Net income to Members $ 90,707 $ 233,990 $ 270,338 $ 371,185

Goodwill Goodwill (Tables)

Goodwill Goodwill (Tables)	9 Months Ended
	Sep. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table presents a reconciliation of the carrying amount of goodwill by reportable segment for the reporting period: Three and Nine Months Ended September 30, 2018 2017 Natural Gas Transportation Gathering, Processing & Terminalling Total Natural Gas Transportation Gathering, Processing & Terminalling Total (in thousands) Balance at beginning of period $ 255,558 $ 149,280 $ 404,838 $ 255,558 $ 87,730 $ 343,288 Goodwill acquired — — — — 61,550 (1) 61,550 Balance at end of period $ 255,558 $ 149,280 $ 404,838 $ 255,558 $ 149,280 $ 404,838 (1) The $61.6 million of goodwill was recorded in connection with the acquisition of a controlling interest in Deeprock Development on July 20, 2017.

Risk Management (Tables)

Risk Management (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Fair Value of Derivative Contracts	The following table summarizes the fair values of our derivative contracts included in the condensed consolidated balance sheets: Balance Sheet September 30, 2018 December 31, 2017 (in thousands) Crude oil derivative contracts (1) Current assets $ 6,014 $ — Crude oil derivative contracts (2) Current liabilities $ 4,163 $ 2,368 (1) As of September 30, 2018 , the fair value shown for crude oil derivative contracts represents the forward purchase of 3,565,000 barrels which will settle throughout the fourth quarter of 2018 and 2019. (2) As of September 30, 2018 , the fair value shown for crude oil derivative contracts represents the forward sale of 3,163,500 barrels of crude oil which will settle throughout the fourth quarter of 2018 and 2019. As of December 31, 2017 , the fair value shown for crude oil derivative contracts represents the forward sale of 356,000 barrels of crude oil which settled in the first quarter of 2018.
Derivative Contracts Included in Consolidated Statements of Income	The following table summarizes the impact of derivative contracts not designated as hedging contracts for the three and nine months ended September 30, 2018 and 2017 : Location of gain (loss) recognized Amount of gain (loss) recognized in income on derivatives Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands) Crude oil derivative contracts Sales of natural gas, NGLs, and crude oil $ 9,435 $ 175 $ 16,665 $ 1,065 Natural gas derivative contracts Sales of natural gas, NGLs, and crude oil $ — $ (22 ) $ — $ 84 Call option derivative Other income, net $ — $ — $ — $ 1,885
Derivative Instruments Maximum Potential Exposure to Credit Loss	The maximum potential exposure to credit losses on our crude oil derivative contracts at September 30, 2018 was: Asset Position (in thousands) Gross $ 6,014 Netting agreement impact — Cash collateral held — Net exposure $ 6,014
Schedule of Energy Commodity Derivative Contracts Based on Fair Value Hierarchy Established by Codification	The following table summarizes the fair value measurements of our derivative contracts as of September 30, 2018 and December 31, 2017 , based on the fair value hierarchy: Asset Fair Value Measurements Using Total Quoted prices in Significant Significant (in thousands) As of September 30, 2018: Crude oil derivative contracts $ 6,014 $ — $ 6,014 $ — Liability Fair Value Measurements Using Total Quoted prices in Significant Significant (in thousands) As of September 30, 2018: Crude oil derivative contracts $ 4,163 $ — $ 4,163 $ — As of December 31, 2017: Crude oil derivative contracts $ 2,368 $ — $ 2,368 $ —

Long-term Debt (Tables)

Long-term Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule of Debt	Long-term debt consisted of the following at September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Tallgrass Equity revolving credit facility (1) $ — $ 146,000 TEP revolving credit facility 1,051,000 661,000 TEP 4.75% senior notes due October 1, 2023 500,000 — TEP 5.50% senior notes due September 15, 2024 750,000 750,000 TEP 5.50% senior notes due January 15, 2028 750,000 750,000 Less: Deferred financing costs, net (2) (20,793 ) (17,737 ) Plus: Unamortized premium on 2028 Notes 3,467 3,730 Total long-term debt, net $ 3,033,674 $ 2,292,993 (1) On July 26, 2018, Tallgrass Equity repaid all outstanding borrowings and terminated its revolving credit facility. (2) Deferred financing costs, net as presented above relate solely to the Senior Notes (as defined below). Deferred financing costs associated with our revolving credit facilities are presented in noncurrent assets on our condensed consolidated balance sheets.
Schedule of Line of Credit Facility	The following table sets forth the available borrowing capacity under the TEP revolving credit facility as of September 30, 2018 and December 31, 2017 : September 30, 2018 December 31, 2017 (in thousands) Total capacity under the TEP revolving credit facility $ 2,250,000 $ 1,750,000 Less: Outstanding borrowings under the TEP revolving credit facility (1,051,000 ) (661,000 ) Less: Letters of credit issued under the TEP revolving credit facility (94 ) (94 ) Available capacity under the TEP revolving credit facility $ 1,198,906 $ 1,088,906
Carrying Amount and Fair value of Long-term Debt	The following table sets forth the carrying amount and fair value of our long-term debt, which is not measured at fair value in the condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 , but for which fair value is disclosed: Fair Value Quoted prices Significant Significant Total Carrying (in thousands) As of September 30, 2018: Revolving credit facility $ — $ 1,051,000 $ — $ 1,051,000 $ 1,051,000 2023 Notes $ — $ 500,310 $ — $ 500,310 $ 495,637 2024 Notes $ — $ 766,635 $ — $ 766,635 $ 740,969 2028 Notes $ — $ 759,458 $ — $ 759,458 $ 746,068 As of December 31, 2017: Revolving credit facilities $ — $ 807,000 $ — $ 807,000 $ 807,000 2024 Notes $ — $ 771,645 $ — $ 771,645 $ 739,824 2028 Notes $ — $ 758,168 $ — $ 758,168 $ 746,169

Partnership Equity Partnership

Partnership Equity Partnership and Equity - Dividends Declared (Tables)	9 Months Ended
	Sep. 30, 2018
Tallgrass Energy, LP (TGE)
Dividends Declared	The following table details the dividends for the periods indicated: Three Months Ended Date Paid Dividends to Class A Shareholders Dividend per Class A Share (in thousands, except per share amounts) September 30, 2018 November 14, 2018 (1) $ 79,717 $ 0.5100 June 30, 2018 August 14, 2018 77,052 0.4975 March 31, 2018 May 15, 2018 28,316 0.4875 December 31, 2017 February 14, 2018 21,346 0.3675 September 30, 2017 November 14, 2017 20,617 0.3550 June 30, 2017 August 14, 2017 19,891 0.3425 March 31, 2017 May 15, 2017 16,697 0.2875 (1) The dividend announced on October 15, 2018 for the third quarter of 2018 will be paid on November 14, 2018 to Class A shareholders of record at the close of business on October 31, 2018 .
Tallgrass Energy Partners
Dividends Declared	TEP Distributions . The following table shows the distributions for the periods indicated: Distributions Distribution Limited Partner General Partner Three Months Ended Date Paid Incentive Distribution Rights General Partner Units Total (in thousands, except per unit amounts) March 31, 2018 May 15, 2018 $ 71,370 $ 39,816 $ 1,267 $ 112,453 $ 0.9750 December 31, 2017 February 14, 2018 70,638 39,125 1,251 111,014 0.9650 September 30, 2017 November 14, 2017 69,174 37,744 1,219 108,137 0.9450 June 30, 2017 August 14, 2017 67,671 36,342 1,186 105,199 0.9250 March 31, 2017 May 15, 2017 60,486 29,840 1,040 91,366 0.8350 As a result of the TEP Merger, Tallgrass Equity and its wholly-owned subsidiary, Tallgrass Equity Investments, LLC, will receive all distributions paid by TEP for the second quarter of 2018 and subsequent periods.

Revenue from Contracts with C_2

Revenue from Contracts with Customers - (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following tables provide the impact of ASC Topic 606 on our condensed consolidated balance sheet as of September 30, 2018 and the condensed consolidated statements of income for the three and nine months ended September 30, 2018 : September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Unconsolidated investments $ 1,872,879 $ 1,796,606 $ 76,273 (1) Three Months Ended September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Crude oil transportation services $ 100,226 $ 100,348 $ (122 ) (2) Sales of natural gas, NGLs, and crude oil $ 44,072 $ 45,225 $ (1,153 ) (3) Processing and other revenues $ 25,069 $ 25,630 $ (561 ) (1)(3) Cost of sales $ 28,556 $ 30,248 $ (1,692 ) (2)(3) Equity in earnings of unconsolidated investments $ 76,268 $ 64,704 $ 11,564 (1) Net income attributable to TGE $ 59,550 $ 53,366 $ 6,184 Basic net income per Class A share $ 0.38 $ 0.34 $ 0.04 Diluted net income per Class A share $ 0.38 $ 0.34 $ 0.04 Nine Months Ended September 30, 2018 As currently reported Under previous guidance Impact of ASC Topic 606 (in thousands) Crude oil transportation services $ 286,130 $ 286,136 $ (6 ) (2) Sales of natural gas, NGLs, and crude oil $ 119,467 $ 122,834 $ (3,367 ) (3) Processing and other revenues $ 72,783 $ 75,846 $ (3,063 ) (1)(3) Cost of sales $ 82,601 $ 88,846 $ (6,245 ) (2)(3) Equity in earnings of unconsolidated investments $ 222,857 $ 189,450 $ 33,407 (1) Net income attributable to TGE $ 77,348 $ 67,701 $ 9,647 Basic net income per Class A share $ 0.85 $ 0.74 $ 0.11 Diluted net income per Class A share $ 0.85 $ 0.74 $ 0.11 (1) Reflects the impact on our investment in Rockies Express and the management fee collected by NatGas of the cumulative effect adjustment at Rockies Express, which arose as a result of the allocation of the transaction price to a series of individual performance obligations in certain long-term transportation contracts with tiered-pricing arrangements. The adjustment increases the carrying amount of our investment in Rockies Express to reflect increased equity in earnings and establishes a receivable for the increased management fee revenue that would have been earned by NatGas. (2) Reflects the impact to revenue and cost of sales to value PLA barrels collected under certain crude oil transportation arrangements at their contract inception fair value in revenue and record an associated lower of cost or net realizable value adjustment in cost of sales. (3) Reflects the reclassification of certain gathering and processing fees collected under arrangements determined to be supply arrangements, rather than customer arrangements under ASC 606, to cost of sales and the reclassification of certain commodities retained as consideration for processing services to processing fee revenue.
Disaggregation of Revenue	A summary of our revenue by line of business is as follows: Three Months Ended September 30, 2018 Natural Gas Transportation segment Crude Oil Transportation segment Gathering, Processing, & Terminalling segment Corporate and Other Total Revenue (in thousands) Crude oil transportation - committed shipper revenue $ — $ 100,614 $ — $ — $ 100,614 Natural gas transportation - firm service 31,070 — — (793 ) 30,277 Water business services — — 12,837 — 12,837 Natural gas gathering & processing fees — — 6,631 — 6,631 All other (1) 2,551 13,321 6,709 (17,636 ) 4,945 Total service revenue 33,621 113,935 26,177 (18,429 ) 155,304 Natural gas liquids sales — — 26,201 — 26,201 Natural gas sales 456 — 5,517 — 5,973 Crude oil sales — 2,315 147 — 2,462 Total commodity sales revenue 456 2,315 31,865 — 34,636 Total revenue from contracts with customers 34,077 116,250 58,042 (18,429 ) 189,940 Other revenue (2) — — 13,570 (3,190 ) 10,380 Total revenue (3) $ 34,077 $ 116,250 $ 71,612 $ (21,619 ) $ 200,320 Nine Months Ended September 30, 2018 Natural Gas Transportation segment Crude Oil Transportation segment Gathering, Processing, & Terminalling segment Corporate and Other Total Revenue (in thousands) Crude oil transportation - committed shipper revenue $ — $ 286,594 $ — $ — $ 286,594 Natural gas transportation - firm service 96,166 — — (4,074 ) 92,092 Water business services — — 38,246 — 38,246 Natural gas gathering & processing fees — — 17,429 — 17,429 All other (1) 8,240 26,124 18,809 (36,832 ) 16,341 Total service revenue 104,406 312,718 74,484 (40,906 ) 450,702 Natural gas liquids sales — — 77,287 — 77,287 Natural gas sales 802 — 17,907 — 18,709 Crude oil sales — 6,290 515 — 6,805 Total commodity sales revenue 802 6,290 95,709 — 102,801 Total revenue from contracts with customers 105,208 319,008 170,193 (40,906 ) 553,503 Other revenue (2) — — 28,869 (9,369 ) 19,500 Total revenue (3) $ 105,208 $ 319,008 $ 199,062 $ (50,275 ) $ 573,003 (1) Includes revenue from crude oil transportation walk up shippers, crude oil terminal services, interruptible natural gas transportation and storage, and natural gas park and loan service. (2) Includes lease and derivative revenue not subject to ASC 606. (3) Excludes $225.8 million and $683.4 million of revenue recognized at Rockies Express for the three and nine months ended September 30, 2018 , respectively. See Note 7 – Investments in Unconsolidated Affiliates for additional information about our investment in Rockies Express.
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	We expect to recognize the total backlog during the remainder of 2018 and future periods as follows (in thousands): Year Estimated Revenue 2018 $ 129,104 2019 496,227 2020 328,066 2021 148,967 2022 136,316 Thereafter 271,512 Total $ 1,510,192
Contract with Customer, Asset and Liability	Contract balances as of September 30, 2018 were as follows: September 30, 2018 January 1, 2018 (in thousands) Accounts receivable from contracts with customers $ 67,603 $ 61,888 Other accounts receivable 168,097 56,727 Accounts receivable, net $ 235,700 $ 118,615 Deferred revenue from contracts with customers (1) $ 103,652 $ 88,471 (1) Revenue recognized during the three and nine months ended September 30, 2018 that was included in the deferred revenue balance at the beginning of the period was $2.0 million and $9.3 million , respectively. This revenue primarily represented the utilization of shipper deficiencies at Pony Express.

Net Income per Class A Share (T

Net Income per Class A Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Summary of Net Income per Class A Share	The following table illustrates the calculation of net income per Class A share for the three and nine months ended September 30, 2018 and 2017 : Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (in thousands, except per unit amounts) Basic Net Income per Class A Share Net income attributable to TGE $ 59,550 $ 15,866 $ 77,348 $ 36,648 Basic weighted average Class A Shares outstanding 155,001 58,075 91,183 58,075 Basic net income per Class A share $ 0.38 $ 0.27 $ 0.85 $ 0.63 Diluted Net Income per Class A Share Net income attributable to TGE $ 59,550 $ 15,866 $ 77,348 $ 36,648 Incremental net income attributable to TGE including the effect of the assumed issuance of Equity Participation Shares 304 64 1,097 132 Net income attributable to TGE including incremental net income from assumed issuance of Equity Participation Shares $ 59,854 $ 15,930 $ 78,445 $ 36,780 Basic weighted average Class A Shares outstanding 155,001 58,075 91,183 58,075 Equity Participation Shares equivalent shares 1,087 117 1,478 118 Diluted weighted average Class A Shares outstanding 156,088 58,192 92,661 58,193 Diluted net income per Class A Share $ 0.38 $ 0.27 $ 0.85 $ 0.63

Reporting Segments (Tables)

Reporting Segments (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Summary of TGE's Segment Information of Revenue	The following tables set forth our segment information for the periods indicated: Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Revenue: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 34,077 $ (816 ) $ 33,261 $ 36,084 $ (1,883 ) $ 34,201 Crude Oil Transportation 116,250 (13,579 ) 102,671 93,029 (6,947 ) 86,082 Gathering, Processing & Terminalling 71,612 (7,224 ) 64,388 57,736 (2,150 ) 55,586 Total revenue $ 221,939 $ (21,619 ) $ 200,320 $ 186,849 $ (10,980 ) $ 175,869 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Revenue: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 105,208 $ (4,136 ) $ 101,072 $ 105,622 $ (4,770 ) $ 100,852 Crude Oil Transportation 319,008 (26,323 ) 292,685 273,768 (6,947 ) 266,821 Gathering, Processing & Terminalling 199,062 (19,816 ) 179,246 121,415 (7,956 ) 113,459 Total revenue $ 623,278 $ (50,275 ) $ 573,003 $ 500,805 $ (19,673 ) $ 481,132
Summary of TGE's Segment Information of Earnings	Three Months Ended September 30, 2018 Three Months Ended September 30, 2017 Tallgrass Equity Adjusted EBITDA: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 121,433 $ (1,460 ) $ 119,973 $ 68,665 $ (530 ) $ 68,135 Crude Oil Transportation 87,567 (5,008 ) 82,559 37,425 (124 ) 37,301 Gathering, Processing & Terminalling 13,679 6,468 20,147 (1,387 ) 654 (733 ) Corporate and Other (2,317 ) — (2,317 ) (9,890 ) — (9,890 ) Reconciliation to Net Income: Add: Equity in earnings of unconsolidated investments (1) 76,268 34,841 Non-cash gain (loss) related to derivative instruments (1) 2,993 (194 ) Gain on disposal of assets (1) 279 — Gain on remeasurement of unconsolidated investment (1) — 2,744 Less: Interest expense, net (1) (34,019 ) (7,966 ) Depreciation and amortization expense (1) (27,356 ) (6,611 ) Distributions from unconsolidated investments (1) (100,720 ) (39,118 ) Non-cash compensation expense (1) (2,767 ) (664 ) Deficiency payments, net (1) (3,468 ) (645 ) Loss on debt retirement (2,245 ) Deferred income tax expense (11,997 ) (12,642 ) Net income attributable to Exchange Right Holders (57,780 ) (48,692 ) Net income attributable to TGE $ 59,550 $ 15,866 Nine Months Ended September 30, 2018 Nine Months Ended September 30, 2017 Tallgrass Equity Adjusted EBITDA: Total Inter- External Total Inter- External (in thousands) Natural Gas Transportation $ 253,169 $ (2,940 ) $ 250,229 $ 133,536 $ (1,349 ) $ 132,187 Crude Oil Transportation 150,943 (3,857 ) 147,086 105,784 2,286 108,070 Gathering, Processing & Terminalling 30,002 6,797 36,799 10,447 (937 ) 9,510 Corporate and Other (20,819 ) — (20,819 ) (25,631 ) — (25,631 ) Reconciliation to Net Income: Add: Equity in earnings of unconsolidated investments (1) 153,235 52,853 Gain on disposal of assets (1) 3,388 376 Non-cash gain related to derivative instruments (1) 3,306 470 Gain on remeasurement of unconsolidated investment (1) — 2,744 Less: Interest expense, net (1) (57,208 ) (20,476 ) Depreciation and amortization expense (1) (45,794 ) (19,218 ) Distributions from unconsolidated investments (1) (198,019 ) (64,848 ) Non-cash compensation expense (1) (4,738 ) (1,614 ) Deficiency payments, net (1) (7,205 ) (7,548 ) Loss on debt retirement (2,245 ) Deferred income tax expense (35,498 ) (24,982 ) Net income attributable to Exchange Right Holders (145,169 ) (105,245 ) Net income attributable to TGE $ 77,348 $ 36,648 (1) Net of noncontrolling interest associated with less than wholly-owned subsidiaries of Tallgrass Equity.
Summary of TGE's Segment Information of Capital Expenditures	Nine Months Ended September 30, Capital Expenditures: 2018 2017 (in thousands) Natural Gas Transportation $ 96,290 $ 9,829 Crude Oil Transportation 39,847 28,785 Gathering, Processing & Terminalling 125,866 49,436 Corporate and Other 3,070 — Total capital expenditures $ 265,073 $ 88,050
Summary of TGE's Segment Information of Assets	Assets: September 30, 2018 December 31, 2017 (in thousands) Natural Gas Transportation $ 2,602,761 $ 1,606,666 Crude Oil Transportation 1,417,853 1,407,758 Gathering, Processing & Terminalling 1,316,487 943,340 Corporate and Other 332,939 334,249 Total assets $ 5,670,040 $ 4,292,013

Description of Business - Addit

Description of Business - Additional Information (Detail)	Jun. 30, 2018shares	Sep. 30, 2018	Jul. 01, 2018	Jan. 01, 2017
Organization [Line Items]
Exchange Ratio	0
Rockies Express Pipeline LLC
Organization [Line Items]
Equity Method Investment, Ownership Percentage		75.00%
Tallgrass NatGas Operator, LLC
Organization [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired				100.00%
Tallgrass Terminals, LLC
Organization [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired				100.00%
Tallgrass Equity, LLC
Organization [Line Items]
Managing Member, Ownership Interest		100.00%
Tallgrass Energy Partners
Organization [Line Items]
Ownership Percentage			100.00%
Ownership Interests Held By Public
Organization [Line Items]
Common Units, Units Outstanding	47,693,097

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 44,100
Unconsolidated investments	$ 1,872,879		$ 909,531
Accounts receivable, net	$ 235,700		$ 118,615
Rockies Express Pipeline LLC
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unconsolidated investments		42,800
Tallgrass NatGas Operator, LLC
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net		1,300
Rockies Express Pipeline LLC
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 125,200

Acquisitions & Dispositions -_2

Acquisitions & Dispositions - Equity Method Investments (Details) - Rockies Express Pipeline LLC - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Feb. 07, 2018
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ (1,108,543)	$ 376,500
Basis Difference, Amortization Period	35 years
Long-term Debt
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ 48,019
Property, Plant and Equipment
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity	$ (1,156,562)
Basis Difference, Amortization Period	35 years
Minimum | Long-term Debt
Schedule of Equity Method Investments [Line Items]
Basis Difference, Amortization Period	2 years
Maximum | Long-term Debt
Schedule of Equity Method Investments [Line Items]
Basis Difference, Amortization Period	25 years

Acquisitions & Dispositions -_3

Acquisitions & Dispositions - BNN North Dakota Acquisition, Assets Acquired & Liabilities Assumed (Details) - USD ($) $ in Thousands	Jan. 12, 2018	Sep. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Inventories		$ 29,317	$ 21,609
Property, plant and equipment, net		2,662,055	2,394,337
Intangible assets, net		$ 132,826	$ 97,731
BNN North Dakota
Business Acquisition [Line Items]
Accounts receivable	$ 2,457
Inventories	67
Property, plant and equipment, net	48,900
Intangible assets, net	46,800
Accounts Payable and Accrued Liabilities	(3,224)
Net identifiable assets acquired (excluding cash)	$ 95,000
Minimum
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	8 years
Maximum
Business Acquisition [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period	14 years

Acquisitions & Dispositions - P

Acquisitions & Dispositions - Pro Forma Revenue & Net Income (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Business Combinations [Abstract]
Pro Forma Revenue	$ 573,431	$ 488,076
Pro Forma Net income attributable to TGE	$ 77,374	$ 36,384

Acquisitions & Dispositions - A

Acquisitions & Dispositions - Additional Information (Details)

Apr. 01, 2018USD ($)

Feb. 23, 2018USD ($)

Feb. 07, 2018USD ($)shares

Feb. 06, 2018USD ($)mi

Feb. 01, 2018USD ($)

Jan. 12, 2018USD ($)a

Jan. 02, 2018USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2018USD ($)

Sep. 30, 2017USD ($)

Dec. 31, 2018

Jan. 01, 2016

Business Acquisition [Line Items]

Payments to acquire equity method investments

$ (444,788,000)

$ (31,570,000)

Sale of Tallgrass Crude Gathering

50,046,000

Payments to Acquire Interest in Subsidiaries and Affiliates

0

400,000,000

Acquisitions

(95,000,000)

$ (57,202,000)

Issuance of Noncontrolling Interest in Subsidiary in Exchange for Membership Interest

$ 31,843,000

Tallgrass Crude Gathering, LLC

Business Acquisition [Line Items]

Ownership Percentage in Subsidiary

100.00%

Miles of gathering pipeline | mi

50

Sale of Tallgrass Crude Gathering

$ 50,000,000

Gain on disposal of assets

$ 9,400,000

BNN North Dakota

Business Acquisition [Line Items]

Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual

$ 13,300,000

Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual

$ 2,900,000

Pony Express Pipeline

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

2.00%

31.30%

Ownership Percentage in Subsidiary

100.00%

Payments to Acquire Interest in Subsidiaries and Affiliates

$ 60,000,000

BNN North Dakota

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

100.00%

Acquisitions

$ (95,000,000)

Acres for Water Gathering and Disposal System | a

133,000

Deeprock Development, LLC

Business Acquisition [Line Items]

Ownership Percentage in Subsidiary

60.00%

Tallgrass Development LP

Business Acquisition [Line Items]

Units Acquired | shares

5,619,218

Tallgrass Development LP | Rockies Express Pipeline LLC

Business Acquisition [Line Items]

Business Acquisition, Percentage of Voting Interests Acquired

25.01%

Pawnee Terminal

Business Acquisition [Line Items]

Equity Method Investment, Ownership Percentage

51.00%

Payments to acquire equity method investments

$ (30,600,000)

Rockies Express Pipeline LLC

Business Acquisition [Line Items]

Equity Method Investment, Ownership Percentage

75.00%

75.00%

Payments to acquire equity method investments

$ (420,328,000)

Basis Difference, Amortization Period

35 years

Equity Method Investment, Difference Between Carrying Amount and Underlying Equity

$ 376,500,000

$ (1,108,543,000)

$ (1,108,543,000)

Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service

2.86%

Iron Horse Pipeline, LLC

Business Acquisition [Line Items]

Equity Method Investment, Ownership Percentage

75.00%

Payments to acquire equity method investments

$ (3,500,000)

Deeprock North, LLC

Business Acquisition [Line Items]

Payments to acquire equity method investments

$ (19,500,000)

$ (19,500,000)

Business Acquisition, Percentage of Voting Interests Acquired

38.00%

Noncontrolling Interest

Business Acquisition [Line Items]

Carrying Value of Common Units

53.8

Capital Unit, Class B | TGE and Tallgrass Equity, LLC

Business Acquisition [Line Items]

Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares

27,554,785

Business Acquisition, Equity Interest Issued or Issuable, Value Assigned

$ 644,800,000

Subsequent Event | Iron Horse Pipeline, LLC

Business Acquisition [Line Items]

Equity Method Investment, Ownership Percentage

51.00%

Subsequent Event | Iron Horse Pipeline, LLC | Silver Creek Midstream, LLC

Business Acquisition [Line Items]

Equity Method Investment, Ownership Percentage

49.00%

Related Party Transactions - Sc

Related Party Transactions - Schedule of Transactions with Affiliated Companies (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related Party Transaction [Line Items]
Revenue from related parties	$ 1,838	$ 3,338	$ 5,603	$ 6,662
Related Party Costs	0	1,062	0	10,476
Operations and maintenance
Related Party Transaction [Line Items]
Expenses related to transactions with related companies	0	7,973	0	21,680
General and administrative expense
Related Party Transaction [Line Items]
Related Party Transaction, Selling, General and Administrative Expenses from Transactions with Related Party	0	11,960	0	32,628
Property, Plant and Equipment
Related Party Transaction [Line Items]
Costs capitalized from transactions with related parties	$ 0	$ 765	$ 0	$ 1,568

Related Party Transactions - _2

Related Party Transactions - Schedule of Balances with Affiliates in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Receivable from related parties	$ 3,369	$ 1,340
Accounts payable to related parties	0	5,342
Rockies Express Pipeline LLC
Related Party Transaction [Line Items]
Receivable from related parties	3,152	1,340
Iron Horse Pipeline, LLC
Related Party Transaction [Line Items]
Receivable from related parties	112	0
Pawnee Terminal, LLC
Related Party Transaction [Line Items]
Receivable from related parties	105	0
Tallgrass Operations, LLC
Related Party Transaction [Line Items]
Accounts payable to related parties	$ 0	$ 5,342

Related Party Transactions - _3

Related Party Transactions - Schedule of Balances of Gas Imbalance with Affiliated Shippers (Detail) - Affiliated Shippers - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Affiliate gas imbalance receivables	$ 17	$ 18
Affiliate gas imbalance payables	$ 689	$ 442

Inventory - (Details)

Inventory - (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Crude oil	$ 18,893	$ 12,792
Materials and supplies	6,359	5,891
Natural gas liquids	364	942
Gas in underground storage	3,701	1,984
Inventory, Net	$ 29,317	$ 21,609

Property Plant and Equipment -

Property Plant and Equipment - Components of Property Plant and Equipment (Detail) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Accumulated depreciation and amortization	$ (356,925,000)	$ (279,192,000)
Property, plant and equipment	2,662,055,000	2,394,337,000
Crude oil pipelines
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,290,868,000	1,220,379,000
Gathering, processing and terminalling assets (1)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	791,766,000	675,092,000
Natural gas pipelines
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	612,729,000	581,400,000
General and other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	125,261,000	98,680,000
Construction work in progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	198,356,000	$ 97,978,000
Deeprock North, LLC | Gathering, processing and terminalling assets (1)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	46,200,000
BNN North Dakota | Gathering, processing and terminalling assets (1)
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 40,100,000

Investments in Unconsolidated_3

Investments in Unconsolidated Affiliates - Equity Method Investments (Details) - Rockies Express Pipeline LLC - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Revenue	$ 225,753	$ 216,756	$ 683,426	$ 625,243
Operating income	127,119	123,965	385,831	344,037
Net income to Members	$ 90,707	$ 233,990	$ 270,338	$ 371,185

Investments in Unconsolidated_4

Investments in Unconsolidated Affiliates (Details) - USD ($)	Jul. 13, 2018	Jul. 12, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Feb. 07, 2018
Schedule of Equity Method Investments [Line Items]
Equity in earnings of unconsolidated investments			$ 76,268,000	$ 123,642,000	$ 222,857,000	$ 187,121,000
Payments to acquire equity method investments					$ (444,788,000)	$ (31,570,000)
Rockies Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments		$ (412,500,000)
Rockies Express Pipeline LLC | Senior Notes
Schedule of Equity Method Investments [Line Items]
Repayments of Senior Debt	$ 550,000,000
Debt Instrument, Interest Rate, Stated Percentage			6.85%		6.85%
Rockies Express Pipeline LLC | Tallgrass Development LP
Schedule of Equity Method Investments [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired							25.01%
Rockies Express Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage			75.00%		75.00%
Equity in earnings of unconsolidated investments					$ 220,308,000
Distributions from unconsolidated investments Unconsolidated Subsidiaries					278,100,000
Payments to acquire equity method investments					$ (420,328,000)

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 404,838	$ 404,838	$ 404,838	$ 343,288
Goodwill, Acquired During Period	0	61,550
Natural Gas Transportation
Goodwill [Line Items]
Goodwill	255,558	255,558	255,558	255,558
Goodwill, Acquired During Period	0	0
Gathering, Processing & Terminalling
Goodwill [Line Items]
Goodwill	149,280	149,280	$ 149,280	$ 87,730
Goodwill, Acquired During Period	$ 0
Deeprock Development, LLC | Gathering, Processing & Terminalling
Goodwill [Line Items]
Goodwill, Acquired During Period		$ 61,550

Risk Management - Schedule of F

Risk Management - Schedule of Fair Value of Derivative Contracts (Detail) - Energy Related Derivative $ in Thousands	Sep. 30, 2018USD ($)bbl	Dec. 31, 2017USD ($)bbl
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	$ 6,014
Derivative liability at fair value	4,163	$ 2,368
Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	6,014	0
Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative liability at fair value	$ 4,163	$ 2,368
Commodity
Derivatives, Fair Value [Line Items]
Derivative, Nonmonetary Notional Amount | bbl		356,000
Commodity | Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative, Nonmonetary Notional Amount | bbl	3,565,000
Commodity | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative, Nonmonetary Notional Amount | bbl	3,163,500

Risk Management - Derivative Co

Risk Management - Derivative Contracts Included in Consolidated Statement of Income (Detail) - Derivatives not designated as hedging contracts - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Energy Related Derivative
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ 9,435	$ 175	$ 16,665	$ 1,065
Energy commodity derivative contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	0	(22)	0	84
Equity Option
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ 0	$ 0	$ 0	$ 1,885

Risk Management - Derivative In

Risk Management - Derivative Instruments Maximum Potential Exposure to Credit Loss (Details) - Energy Related Derivative	Sep. 30, 2018USD ($)
Concentration Risk [Line Items]
Gross	$ 6,014,000
Netting agreement impact	0
Cash collateral held	0
Net exposure	$ 6,014,000

Risk Management - Schedule of E

Risk Management - Schedule of Energy Commodity Derivative Contracts Based on Fair Value Hierarchy Established by Codification (Detail) - Energy Related Derivative - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	$ 6,014
Derivative liability at fair value	4,163	$ 2,368
Quoted prices in active markets for identical assets (Level 1)
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	0
Derivative liability at fair value	0	0
Significant other observable inputs (Level 2)
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	6,014
Derivative liability at fair value	4,163	2,368
Significant unobservable inputs (Level 3)
Derivatives, Fair Value [Line Items]
Derivative asset at fair value	0
Derivative liability at fair value	$ 0	$ 0

Risk Management - Additional In

Risk Management - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Feb. 01, 2017	Jan. 01, 2016	Sep. 30, 2018	Sep. 30, 2017	Feb. 01, 2018
Derivative [Line Items]
Partners' Capital Account, Units, Treasury Units Purchased			736,262
Partial exercise of call option			$ 35,300
Cash in Margin Accounts and Outstanding Letters of Credit	1.1	3
Pony Express Pipeline
Derivative [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired				31.30%			2.00%
Equity Option
Derivative [Line Items]
Partners' Capital Account, Units, Treasury Units Purchased			1,703,094
Partial exercise of call option			$ 72,400		$ 0	$ 72,381
Equity Option | Pony Express Pipeline
Derivative [Line Items]
Derivative, Term of Contract				18 months
Option Indexed to Issuer's Equity, Strike Price				$ 42.50
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares				6,518,000

Long-term Debt - Schedule of De

Long-term Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Less: Deferred financing costs, net	$ (20,793)	$ (17,737)
Total long-term debt, net	3,033,674	2,292,993
Revolving Credit Facility
Debt Instrument [Line Items]
Total long-term debt, net	1,051,000	807,000
Tallgrass Equity, LLC | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	0	146,000
Tallgrass Energy Partners
Debt Instrument [Line Items]
Plus: Unamortized premium on 2028 Notes	3,467	3,730
Tallgrass Energy Partners | Revolving Credit Facility
Debt Instrument [Line Items]
Long-term Debt, Gross	1,051,000	661,000
Total long-term debt, net	1,051,000	661,000
2023 Senior Notes
Debt Instrument [Line Items]
Total long-term debt, net	495,637
2023 Senior Notes | Tallgrass Energy Partners | Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	500,000	0
2024 Senior Notes
Debt Instrument [Line Items]
Total long-term debt, net	740,969	739,824
2024 Senior Notes | Tallgrass Energy Partners | Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	750,000	750,000
2028 Senior Notes
Debt Instrument [Line Items]
Total long-term debt, net	746,068	746,169
2028 Senior Notes | Tallgrass Energy Partners | Senior Notes
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 750,000	$ 750,000

Long-term Debt - Capacity under

Long-term Debt - Capacity under Revolving Credit Facility - TEP (Details) - USD ($)	Sep. 30, 2018	Jul. 26, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Long-term Debt	$ (3,033,674,000)		$ (2,292,993,000)
Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	(1,051,000,000)		(807,000,000)
Tallgrass Energy Partners | Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt	(1,051,000,000)		(661,000,000)
Letters of Credit Outstanding, Amount	(94,000)		(94,000)
Line of Credit Facility, Remaining Borrowing Capacity	1,198,906,000		1,088,906,000
Wells Fargo Bank, National Association | Tallgrass Energy Partners | Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,250,000,000	$ 2,250,000,000	$ 1,750,000,000

Long-term Debt - Carrying Amoun

Long-term Debt - Carrying Amount and Fair Value of Long-term Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt	$ 3,033,674	$ 2,292,993
2023 Senior Notes
Debt Instrument [Line Items]
Fair Value	500,310
Long-term Debt	495,637
2023 Senior Notes | Quoted prices in active markets for identical assets (Level 1)
Debt Instrument [Line Items]
Fair Value	0
2023 Senior Notes | Significant other observable inputs (Level 2)
Debt Instrument [Line Items]
Fair Value	500,310
2023 Senior Notes | Significant unobservable inputs (Level 3)
Debt Instrument [Line Items]
Fair Value	0
2024 Senior Notes
Debt Instrument [Line Items]
Fair Value	766,635	771,645
Long-term Debt	740,969	739,824
2024 Senior Notes | Quoted prices in active markets for identical assets (Level 1)
Debt Instrument [Line Items]
Fair Value	0	0
2024 Senior Notes | Significant other observable inputs (Level 2)
Debt Instrument [Line Items]
Fair Value	766,635	771,645
2024 Senior Notes | Significant unobservable inputs (Level 3)
Debt Instrument [Line Items]
Fair Value	0	0
2028 Senior Notes
Debt Instrument [Line Items]
Fair Value	759,458	758,168
Long-term Debt	746,068	746,169
2028 Senior Notes | Quoted prices in active markets for identical assets (Level 1)
Debt Instrument [Line Items]
Fair Value	0	0
2028 Senior Notes | Significant other observable inputs (Level 2)
Debt Instrument [Line Items]
Fair Value	759,458	758,168
2028 Senior Notes | Significant unobservable inputs (Level 3)
Debt Instrument [Line Items]
Fair Value	0	0
Revolving Credit Facility
Debt Instrument [Line Items]
Fair Value	1,051,000	807,000
Long-term Debt	1,051,000	807,000
Revolving Credit Facility | Quoted prices in active markets for identical assets (Level 1)
Debt Instrument [Line Items]
Fair Value	0	0
Revolving Credit Facility | Significant other observable inputs (Level 2)
Debt Instrument [Line Items]
Fair Value	1,051,000	807,000
Revolving Credit Facility | Significant unobservable inputs (Level 3)
Debt Instrument [Line Items]
Fair Value	$ 0	$ 0

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail)	Sep. 26, 2018USD ($)	Jul. 26, 2018USD ($)	Dec. 11, 2017USD ($)	Sep. 15, 2017USD ($)	May 16, 2017USD ($)	Sep. 01, 2016USD ($)	Jul. 25, 2018	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt								$ 500,000,000	$ 850,000,000
Debt, Weighted Average Interest Rate								3.54%
Debt Instrument, Interest Rate, Effective Percentage								3.98%
Maximum | Wells Fargo Bank, National Association
Debt Instrument [Line Items]
Credit facility commitment fee		0.375%					0.50%
Minimum | Wells Fargo Bank, National Association
Debt Instrument [Line Items]
Credit facility commitment fee		0.25%					0.25%
Tallgrass Energy Partners | Revolving Credit Facility | Wells Fargo Bank, National Association
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 2,250,000,000						$ 2,250,000,000		$ 1,750,000,000
Tallgrass Energy Partners | Maximum | Revolving Credit Facility | Wells Fargo Bank, National Association
Debt Instrument [Line Items]
Consolidated leverage ratio		5.50					5
Consolidated Senior Secured Leverage Ratio One								3.75
Tallgrass Energy Partners | Minimum | Revolving Credit Facility | Wells Fargo Bank, National Association
Debt Instrument [Line Items]
Consolidated Interest Coverage Ratio One								2.50
Senior Notes | Tallgrass Energy Partners
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								5.50%
2023 Senior Notes | Senior Notes | Tallgrass Energy Partners
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt	$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage								4.75%
2028 Senior Notes | Senior Notes | Tallgrass Energy Partners
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt			$ 250,000,000	$ 500,000,000
2024 Senior Notes | Senior Notes | Tallgrass Energy Partners
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt					$ 350,000,000	$ 400,000,000

Partnership Equity - TGE Summar

Partnership Equity - TGE Summary of Dividends (Details) - Tallgrass Energy, LP (TGE) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Dividends Payable [Line Items]
Dividends	$ 79,717	$ 77,052	$ 28,316	$ 21,346	$ 20,617	$ 19,891	$ 16,697
Dividends Payable, Amount Per Share	$ 0.5100	$ 0.4975	$ 0.4875	$ 0.3675	$ 0.3550	$ 0.3425	$ 0.2875

Partnership Equity - TEP Summar

Partnership Equity - TEP Summary of Distributions (Details) - Tallgrass Energy Partners - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Distribution Made to Limited Partner [Line Items]
Limited Partner Common Units	$ 71,370	$ 70,638	$ 69,174	$ 67,671	$ 60,486
Incentive Distribution Rights	39,816	39,125	37,744	36,342	29,840
General Partner Units	1,267	1,251	1,219	1,186	1,040
Total Distributions	$ (112,453)	$ (111,014)	$ (108,137)	$ (105,199)	$ (91,366)
Distribution Made to Limited Partner, Distributions Paid, Per Unit	$ 0.9750	$ 0.9650	$ 0.9450	$ 0.9250	$ 0.8350

Partnership Equity - Additional

Partnership Equity - Additional Information (Detail) - USD ($)	Feb. 07, 2018	Feb. 01, 2017	Oct. 31, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Units, Treasury Units Purchased		736,262
Payments for Repurchase of Common Stock		$ 35,300,000
Treasury Stock Acquired, Average Cost Per Share		$ 47.99
Distributions to noncontrolling interests									$ (262,856,000)	$ (229,710,000)
Payments for Purchase of Common Stock									(198,000,000)
Tallgrass Energy Partners
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Units, Sold in Public Offering										2,341,061
SharesIssuedWeightedAveragePricePerShare										$ 48.82
Issuance of TEP common units to the public, net of offering costs										$ 112,400,000
LimitedPartnerOfferingCosts										1,900,000
Payments for Repurchase of Common Stock									$ 0	35,335,000
Partners' Capital Account, Distributions				$ 112,453,000	$ 111,014,000	$ 108,137,000	$ 105,199,000	$ 91,366,000
Tallgrass Equity, LLC
Limited Partners' Capital Account [Line Items]
Equity interest held by noncontrolling interests									44.36%
Deeprock Development, LLC
Limited Partners' Capital Account [Line Items]
Equity interest held by noncontrolling interests									40.00%
Tallgrass Development LP
Limited Partners' Capital Account [Line Items]
Units Acquired	5,619,218
Tallgrass Development LP | Rockies Express Pipeline LLC
Limited Partners' Capital Account [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired	25.01%
Noncontrolling Interest
Limited Partners' Capital Account [Line Items]
Contributions from noncontrolling interest									$ 183,000	1,093,000
Distributions to noncontrolling interests									(262,856,000)	(229,710,000)
Tallgrass Equity distributions to noncontrolling interests									160,600,000	90,000,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders									4,600,000	4,300,000
Carrying Value of Common Units	53.8
Contributions from TD										1,451,000
Noncontrolling Interest | Tallgrass Energy Partners
Limited Partners' Capital Account [Line Items]
Issuance of TEP common units to the public, net of offering costs									(279,000)	101,043,000
Payments for Repurchase of Common Stock										(31,717,000)
Partners' Capital Account, Distributions									(97,700,000)	(135,400,000)
Noncontrolling Interest | Deeprock Development, LLC
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Acquisitions										45,869,000
Noncontrolling Interest | Rockies Express Pipeline LLC
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Acquisitions									74,421,000	40,159,000
Total Partner Equity Including Portion Attributable to Noncontrolling Interest
Limited Partners' Capital Account [Line Items]
Contributions from noncontrolling interest									183,000	1,093,000
Distributions to noncontrolling interests									(262,856,000)	(229,710,000)
Contributions from TD										2,301,000
Total Partner Equity Including Portion Attributable to Noncontrolling Interest | Tallgrass Energy Partners
Limited Partners' Capital Account [Line Items]
Issuance of TEP common units to the public, net of offering costs									(377,000)	112,393,000
Payments for Repurchase of Common Stock										(35,335,000)
Total Partner Equity Including Portion Attributable to Noncontrolling Interest | Deeprock Development, LLC
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Acquisitions										45,869,000
Total Partner Equity Including Portion Attributable to Noncontrolling Interest | Rockies Express Pipeline LLC
Limited Partners' Capital Account [Line Items]
Partners' Capital Account, Acquisitions									$ 108,537,000	$ 63,681,000
Common Class A
Limited Partners' Capital Account [Line Items]
Conversion of Stock, Shares Issued									2,403,766
Subsequent Event | Common Class A
Limited Partners' Capital Account [Line Items]
Conversion of Stock, Shares Issued			417,566

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Impact of Adoption (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unconsolidated investments	$ 1,872,879		$ 1,872,879		$ 909,531
Revenues	(200,320)	$ (175,869)	(573,003)	$ (481,132)
Equity in earnings of unconsolidated investments	76,268	123,642	222,857	187,121
Net income attributable to TGE	$ 59,550	$ 15,866	$ 77,348	$ 36,648
Basic net income per Class A share	$ 0.38	$ 0.27	$ 0.85	$ 0.63
Diluted net income per Class A share	$ 0.38	$ 0.27	$ 0.85	$ 0.63
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unconsolidated investments	$ 1,796,606		$ 1,796,606
Equity in earnings of unconsolidated investments	64,704		189,450
Net income attributable to TGE	$ 53,366		$ 67,701
Basic net income per Class A share	$ 0.34		$ 0.74
Diluted net income per Class A share	$ 0.34		$ 0.74
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Unconsolidated investments	$ 76,273		$ 76,273
Equity in earnings of unconsolidated investments	11,564		33,407
Net income attributable to TGE	$ 6,184		$ 9,647
Basic net income per Class A share	$ 0.04		$ 0.11
Diluted net income per Class A share	$ 0.04		$ 0.11
Crude oil transportation services
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ (100,226)	$ (86,180)	$ (286,130)	$ (260,366)
Crude oil transportation services | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(100,348)		(286,136)
Crude oil transportation services | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(122)		(6)
Sales of natural gas, NGLs, and crude oil
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(44,072)	(32,215)	(119,467)	(70,514)
Sales of natural gas, NGLs, and crude oil | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(45,225)		(122,834)
Sales of natural gas, NGLs, and crude oil | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(1,153)		(3,367)
Processing and other revenues
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(25,069)	(27,218)	(72,783)	(58,882)
Processing and other revenues | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(25,630)		(75,846)
Processing and other revenues | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	(561)		(3,063)
Cost of Sales
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of sales and transportation services	28,556	$ 26,984	82,601	$ 58,740
Cost of Sales | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of sales and transportation services	30,248		88,846
Cost of Sales | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Cost of sales and transportation services	$ (1,692)		$ (6,245)

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 200,320		$ 573,003
Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	100,614		286,594
Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	30,277		92,092
Water business services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,837		38,246
Natural Gas Gathering & Processing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,631		17,429
Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,945		16,341
Service Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	155,304		450,702
Natural Gas Liquids
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,201		77,287
Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,973		18,709
Crude Oil
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,462		6,805
Energy Commodities and Service
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	34,636		102,801
Total Service and Commodity Sales Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	189,940		553,503
Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	10,380		19,500
Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	34,077		105,208
Natural Gas Transportation | Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Natural Gas Transportation | Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	31,070		96,166
Natural Gas Transportation | Water business services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Natural Gas Transportation | Natural Gas Gathering & Processing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Natural Gas Transportation | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,551		8,240
Natural Gas Transportation | Service Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	33,621		104,406
Natural Gas Transportation | Natural Gas Liquids
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Natural Gas Transportation | Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	456		802
Natural Gas Transportation | Crude Oil
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Natural Gas Transportation | Energy Commodities and Service
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	456		802
Natural Gas Transportation | Total Service and Commodity Sales Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	34,077		105,208
Natural Gas Transportation | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	116,250		319,008
Crude Oil Transportation | Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	100,614		286,594
Crude Oil Transportation | Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation | Water business services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation | Natural Gas Gathering & Processing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13,321		26,124
Crude Oil Transportation | Service Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	113,935		312,718
Crude Oil Transportation | Natural Gas Liquids
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation | Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Crude Oil Transportation | Crude Oil
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,315		6,290
Crude Oil Transportation | Energy Commodities and Service
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,315		6,290
Crude Oil Transportation | Total Service and Commodity Sales Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	116,250		319,008
Crude Oil Transportation | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Gathering, Processing & Terminalling
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	71,612		199,062
Gathering, Processing & Terminalling | Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Gathering, Processing & Terminalling | Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Gathering, Processing & Terminalling | Water business services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12,837		38,246
Gathering, Processing & Terminalling | Natural Gas Gathering & Processing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,631		17,429
Gathering, Processing & Terminalling | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6,709		18,809
Gathering, Processing & Terminalling | Service Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,177		74,484
Gathering, Processing & Terminalling | Natural Gas Liquids
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,201		77,287
Gathering, Processing & Terminalling | Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,517		17,907
Gathering, Processing & Terminalling | Crude Oil
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	147		515
Gathering, Processing & Terminalling | Energy Commodities and Service
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	31,865		95,709
Gathering, Processing & Terminalling | Total Service and Commodity Sales Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58,042		170,193
Gathering, Processing & Terminalling | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13,570		28,869
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(21,619)		(50,275)
Corporate and Other | Crude Oil Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Natural Gas Transportation
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(793)		(4,074)
Corporate and Other | Water business services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Natural Gas Gathering & Processing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(17,636)		(36,832)
Corporate and Other | Service Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(18,429)		(40,906)
Corporate and Other | Natural Gas Liquids
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Natural Gas
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Crude Oil
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Energy Commodities and Service
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0		0
Corporate and Other | Total Service and Commodity Sales Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(18,429)		(40,906)
Corporate and Other | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(3,190)		(9,369)
Rockies Express Pipeline LLC
Disaggregation of Revenue [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue	$ 225,753	$ 216,756	$ 683,426	$ 625,243

Revenue from Contract with Cust

Revenue from Contract with Customer - Remaining Performance Obligation (Details) $ in Thousands	Sep. 30, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 months
Revenue, Remaining Performance Obligation, Amount	$ 129,104
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 496,227
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 328,066
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 148,967
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Amount	$ 136,316
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	15 years
Revenue, Remaining Performance Obligation, Amount	$ 1,510,192

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset, Net, Current	$ 67,603	$ 67,603	$ 61,888
Accounts and Other Receivables, Net, Current	168,097	168,097	56,727
Accounts receivable, net	235,700	235,700	118,615
Deferred revenue	103,652	103,652	$ 88,471
Contract with Customer, Liability, Revenue Recognized	$ 2,000	$ 9,300

Net Income per Class A Share (D

Net Income per Class A Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income attributable to TGE	$ 59,550	$ 15,866	$ 77,348	$ 36,648
Basic average number of Class A shares outstanding	155,001	58,075	91,183	58,075
Basic net income per Class A share	$ 0.38	$ 0.27	$ 0.85	$ 0.63
Incremental net income attributable to TGE including the effect of the assumed issuance of Equity Participation Shares	$ 304	$ 64	$ 1,097	$ 132
Net income attributable to TGE including incremental net income from assumed issuance of Equity Participation Shares	$ 59,854	$ 15,930	$ 78,445	$ 36,780
Equity Participation Shares equivalent shares	1,087	117	1,478	118
Diluted average number of Class A shares outstanding	156,088	58,192	92,661	58,193
Diluted net income per Class A Share	$ 0.38	$ 0.27	$ 0.85	$ 0.63

Net Income Per Class A Share -

Net Income Per Class A Share - Additional Information (Details) $ / shares in Units, $ in Millions	Jun. 30, 2018	Sep. 30, 2018USD ($)$ / sharesshares
Earnings Per Share [Abstract]
Exchange Ratio	0
Nonvested Equity Participation Shares | shares		1,968,908
Nonvested, Weighted Average Grant Date Fair Value | $ / shares		$ 18.93
Nonvested Awards, Compensation Cost Not yet Recognized | $		$ 19.6
Weighted Average Remaining Contractual Terms		2 years 11 months

Regulatory Matters (Details)

Regulatory Matters (Details)	9 Months Ended
	Sep. 30, 2018Bcf / dmi	Jul. 01, 2018	Jul. 01, 2017
Public Utilities, General Disclosures [Line Items]
Capacity Enhancement | Bcf / d	0.8
Miles of Pipeline | mi	70
Size of Pipeline	36
Pony Express Pipeline
Public Utilities, General Disclosures [Line Items]
FERC Annual Index Adjustment		4.40%	0.20%

Legal and Environmental Matte_2

Legal and Environmental Matters - Additional Information (Detail)	Jul. 12, 2017USD ($)	Jan. 12, 2017USD ($)Bcf / d	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2016Bcf / dmi	Dec. 31, 2015mi	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Apr. 14, 2016USD ($)
Loss Contingencies [Line Items]
Environmental accruals			$ 7,500,000					$ 7,700,000	$ 7,700,000
Cost of Services, Environmental Remediation (Deprecated 2018-01-31)								$ 21,800,000
Aggregate cost of crack tool runs									$ 18,000,000
General Partner
Loss Contingencies [Line Items]
Contributions from TD							$ 20,000,000
Trailblazer
Loss Contingencies [Line Items]
Miles of Natural Gas Pipeline Needing Repair or Replacement | mi					8
Trailblazer | Minimum
Loss Contingencies [Line Items]
Miles of Natural Gas Pipeline Needing Repair or Replacement | mi						25
Trailblazer | Maximum
Loss Contingencies [Line Items]
Miles of Natural Gas Pipeline Needing Repair or Replacement | mi						35
Tallgrass Development LP
Loss Contingencies [Line Items]
Contractual indemnity provided to TEP by TD			20,000,000
Annual deductible			$ 1,500,000
Subsequent Event
Loss Contingencies [Line Items]
Total Remediation costs				$ 6,100,000
Remediation costs, Anticipated costs				$ 20,000,000
Ultra Resources Complaint
Loss Contingencies [Line Items]
Firm transportation service agreement | Bcf / d		0.2			0.2
Gain Contingency, Unrecorded Amount										$ 303,000,000
Litigation Settlement, Amount Awarded from Other Party	$ 150,000,000
Firm Transportation Rate		$ 0.37
Anticipated Annual Revenue		$ 26,800,000

Reporting Segments - Summary of

Reporting Segments - Summary of TGE's Segment Information of Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total Revenues	$ 200,320	$ 175,869	$ 573,003	$ 481,132
TGE
Segment Reporting Information [Line Items]
Total Revenues	200,320	175,869	573,003	481,132
TGE | Natural Gas Transportation
Segment Reporting Information [Line Items]
Total Revenues	33,261	34,201	101,072	100,852
TGE | Crude Oil Transportation
Segment Reporting Information [Line Items]
Total Revenues	102,671	86,082	292,685	266,821
TGE | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Total Revenues	64,388	55,586	179,246	113,459
TGE | Operating Segments
Segment Reporting Information [Line Items]
Total Revenues	221,939	186,849	623,278	500,805
TGE | Operating Segments | Natural Gas Transportation
Segment Reporting Information [Line Items]
Total Revenues	34,077	36,084	105,208	105,622
TGE | Operating Segments | Crude Oil Transportation
Segment Reporting Information [Line Items]
Total Revenues	116,250	93,029	319,008	273,768
TGE | Operating Segments | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Total Revenues	71,612	57,736	199,062	121,415
TGE | Inter-Segment
Segment Reporting Information [Line Items]
Total Revenues	(21,619)	(10,980)	(50,275)	(19,673)
TGE | Inter-Segment | Natural Gas Transportation
Segment Reporting Information [Line Items]
Total Revenues	(816)	(1,883)	(4,136)	(4,770)
TGE | Inter-Segment | Crude Oil Transportation
Segment Reporting Information [Line Items]
Total Revenues	(13,579)	(6,947)	(26,323)	(6,947)
TGE | Inter-Segment | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Total Revenues	$ (7,224)	$ (2,150)	$ (19,816)	$ (7,956)

Reporting Segments - Summary _2

Reporting Segments - Summary of TGE's Segment Information of Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation to Net Income:
Equity in earnings of unconsolidated investments	$ (76,268)	$ (123,642)	$ (222,857)	$ (187,121)
Gain (Loss) on Disposition of Assets	(279)	0	(9,417)	(1,264)
Interest expense, net	34,019	24,408	95,062	61,539
Depreciation and amortization	(27,595)	(23,782)	(81,408)	(67,276)
Distributions from unconsolidated investments			(222,082)	(187,624)
Deferred income tax expense	11,997	12,642	35,498	24,982
Net Income (Loss) Attributable to Noncontrolling Interest	59,162	154,911	265,378	280,534
Net income attributable to TGE	59,550	15,866	77,348	36,648
TGE
Reconciliation to Net Income:
Net income attributable to TGE	59,550	(15,866)	77,348	36,648
TGE | Natural Gas Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	119,973	68,135	250,229	132,187
TGE | Crude Oil Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	82,559	37,301	147,086	108,070
TGE | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	20,147	(733)	36,799	9,510
TGE | Corporate and Other
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	(2,317)	(9,890)	(20,819)	(25,631)
TGE | Operating Segments | Natural Gas Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	121,433	68,665	253,169	133,536
TGE | Operating Segments | Crude Oil Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	87,567	37,425	150,943	105,784
TGE | Operating Segments | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	13,679	(1,387)	30,002	10,447
TGE | Operating Segments | Corporate and Other
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	(2,317)	(9,890)	(20,819)	(25,631)
TGE | Inter-Segment | Natural Gas Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	(1,460)	(530)	(2,940)	(1,349)
TGE | Inter-Segment | Crude Oil Transportation
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	(5,008)	(124)	(3,857)	2,286
TGE | Inter-Segment | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	6,468	654	6,797	(937)
TGE | Inter-Segment | Corporate and Other
Segment Reporting Information [Line Items]
Adjusted Earnings Before Interest Taxes Depreciation And Amortization	0	0	0	0
TGE | Segment Reconciling Items
Reconciliation to Net Income:
Equity in earnings of unconsolidated investments	76,268	(34,841)	153,235	(52,853)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(2,993)	194	(3,306)	(470)
Gain (Loss) on Disposition of Assets	279	0	3,388	376
Gain on remeasurement of unconsolidated investment	0	2,744	0	2,744
Interest expense, net	(34,019)	(7,966)	(57,208)	(20,476)
Depreciation and amortization	(27,356)	(6,611)	(45,794)	(19,218)
Distributions from unconsolidated investments	(100,720)	(39,118)	(198,019)	(64,848)
Share-based Compensation	(2,767)	(664)	(4,738)	(1,614)
Deficiency Payments	(3,468)	(645)	(7,205)	(7,548)
Loss on debt retirement	(2,245)		(2,245)
Deferred income tax expense	11,997	12,642	35,498	24,982
Exchange Right Holders | TGE | Segment Reconciling Items
Reconciliation to Net Income:
Net Income (Loss) Attributable to Noncontrolling Interest	$ (57,780)	$ (48,692)	$ (145,169)	$ (105,245)

Reporting Segments - Summary _3

Reporting Segments - Summary of TGE's Segment Information for Payments to Acquire Plant, Property and Equipment (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Capital expenditures	$ 265,073	$ 88,050
TGE
Segment Reporting Information [Line Items]
Capital expenditures	265,073	88,050
TGE | Natural Gas Transportation
Segment Reporting Information [Line Items]
Capital expenditures	96,290	9,829
TGE | Crude Oil Transportation
Segment Reporting Information [Line Items]
Capital expenditures	39,847	28,785
TGE | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Capital expenditures	125,866	49,436
TGE | Corporate and Other
Segment Reporting Information [Line Items]
Capital expenditures	$ 3,070	$ 0

Reporting Segments - Summary _4

Reporting Segments - Summary of TGE's Segment Information of Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Segment assets	$ 5,670,040	$ 4,292,013
TGE
Segment Reporting Information [Line Items]
Segment assets	5,670,040	4,292,013
TGE | Natural Gas Transportation
Segment Reporting Information [Line Items]
Segment assets	2,602,761	1,606,666
TGE | Crude Oil Transportation
Segment Reporting Information [Line Items]
Segment assets	1,417,853	1,407,758
TGE | Gathering, Processing & Terminalling
Segment Reporting Information [Line Items]
Segment assets	1,316,487	943,340
TGE | Corporate and Other
Segment Reporting Information [Line Items]
Segment assets	$ 332,939	$ 334,249

Reporting Segments - Additional

Reporting Segments - Additional Information (Detail) - Segment	9 Months Ended
	Sep. 30, 2018	Feb. 07, 2018
Segment Reporting Information [Line Items]
Number of reportable segments	3
Rockies Express Pipeline LLC | Tallgrass Development LP
Segment Reporting Information [Line Items]
Business Acquisition, Percentage of Voting Interests Acquired		25.01%
Rockies Express Pipeline LLC
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	75.00%