InfraREIT (HIFR) 10-Q 1 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 29, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Trading Symbol	HIFR
Entity Registrant Name	InfraREIT, Inc.
Entity Central Index Key	1,506,401
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		43,962,167

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 3,223	$ 2,867
Restricted cash	1,687	1,683
Due from affiliates	33,401	35,172
Inventory	7,592	6,759
Prepaids and other current assets	1,041	2,460
Total current assets	46,944	48,941
Electric Plant, net	1,800,517	1,772,229
Goodwill	138,384	138,384
Other Assets	31,771	34,314
Total Assets	2,017,616	1,993,868
Current Liabilities
Accounts payable and accrued liabilities	28,345	21,230
Short-term borrowings	101,000	41,000
Current portion of long-term debt	8,667	68,305
Dividends and distributions payable	15,176	15,169
Accrued taxes	748	5,633
Total current liabilities	153,936	151,337
Long-Term Debt, Less Deferred Financing Costs	834,693	841,215
Regulatory Liabilities	111,811	100,458
Total liabilities	1,100,440	1,093,010
Commitments and Contingencies
Equity
Common stock, $0.01 par value; 450,000,000 shares authorized; 43,962,167 and 43,796,915 issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	440	438
Additional paid-in capital	709,488	706,357
Accumulated deficit	(38,229)	(49,728)
Total InfraREIT, Inc. equity	671,699	657,067
Noncontrolling interest	245,477	243,791
Total equity	917,176	900,858
Total Liabilities and Equity	$ 2,017,616	$ 1,993,868

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par or stated value per share	$ 0.01	$ 0.01
Common stock, shares authorized	450,000,000	450,000,000
Common stock, shares issued	43,962,167	43,796,915
Common stock, shares, outstanding	43,962,167	43,796,915

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Lease revenue	$ 48,926	$ 51,618	$ 142,409	$ 131,664
Operating costs and expenses
General and administrative expense	6,787	6,718	19,506	19,565
Depreciation	12,063	13,328	35,632	38,997
Total operating costs and expenses	18,850	20,046	55,138	58,562
Income from operations	30,076	31,572	87,271	73,102
Other (expense) income
Interest expense, net	(10,120)	(10,357)	(31,864)	(30,196)
Other income, net	7	331	1,114	351
Total other expense	(10,113)	(10,026)	(30,750)	(29,845)
Income before income taxes	19,963	21,546	56,521	43,257
Income tax expense (benefit)	257	308	(4,885)	873
Net income	19,706	21,238	61,406	42,384
Less: Net income attributable to noncontrolling interest	5,435	5,908	16,937	11,797
Net income attributable to InfraREIT, Inc.	$ 14,271	$ 15,330	$ 44,469	$ 30,587
Net income attributable to InfraREIT, Inc. common stockholders per share:
Basic	$ 0.32	$ 0.35	$ 1.01	$ 0.70
Diluted	0.32	0.35	1.01	0.70
Cash dividends declared per common share	$ 0.25	$ 0.25	$ 0.75	$ 0.75

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total InfraREIT, Inc. Equity	Noncontrolling Interest
Balance at Dec. 31, 2016	$ 943,911	$ 438	$ 705,845	$ (18,243)	$ 688,040	$ 255,871
Balance, shares at Dec. 31, 2016		43,772,283
Dividends and distributions	(15,169)			(10,944)	(10,944)	(4,225)
Redemption of operating partnership units for common stock			55		55	(55)
Redemption of operating partnership units for common stock, shares		3,100
Net income	11,017			7,949	7,949	3,068
Equity based compensation	140					140
Balance at Mar. 31, 2017	939,899	$ 438	705,900	(21,238)	685,100	254,799
Balance, shares at Mar. 31, 2017		43,775,383
Balance at Dec. 31, 2016	$ 943,911	$ 438	705,845	(18,243)	688,040	255,871
Balance, shares at Dec. 31, 2016		43,772,283
Redemption of operating partnership units for common stock, shares	23,349
Net income	$ 42,384
Balance at Sep. 30, 2017	941,216	$ 438	706,337	(20,494)	686,281	254,935
Balance, shares at Sep. 30, 2017		43,795,632
Balance at Mar. 31, 2017	939,899	$ 438	705,900	(21,238)	685,100	254,799
Balance, shares at Mar. 31, 2017		43,775,383
Dividends and distributions	(15,169)			(10,944)	(10,944)	(4,225)
Redemption of operating partnership units for common stock			55		55	(55)
Redemption of operating partnership units for common stock, shares		3,107
Net income	10,129			7,308	7,308	2,821
Equity based compensation	145					145
Balance at Jun. 30, 2017	935,004	$ 438	705,955	(24,874)	681,519	253,485
Balance, shares at Jun. 30, 2017		43,778,490
Dividends and distributions	(15,169)			(10,950)	(10,950)	(4,219)
Redemption of operating partnership units for common stock			382		382	(382)
Redemption of operating partnership units for common stock, shares		17,142
Net income	21,238			15,330	15,330	5,908
Equity based compensation	143					143
Balance at Sep. 30, 2017	941,216	$ 438	706,337	(20,494)	686,281	254,935
Balance, shares at Sep. 30, 2017		43,795,632
Balance at Dec. 31, 2017	900,858	$ 438	706,357	(49,728)	657,067	243,791
Balance, shares at Dec. 31, 2017		43,796,915
Dividends and distributions	(15,176)			(10,990)	(10,990)	(4,186)
Redemption of operating partnership units for common stock		$ 2	3,104		3,106	(3,106)
Redemption of operating partnership units for common stock, shares		163,969
Net income	17,764			12,864	12,864	4,900
Equity based compensation	140					140
Balance at Mar. 31, 2018	903,586	$ 440	709,461	(47,854)	662,047	241,539
Balance, shares at Mar. 31, 2018		43,960,884
Balance at Dec. 31, 2017	$ 900,858	$ 438	706,357	(49,728)	657,067	243,791
Balance, shares at Dec. 31, 2017		43,796,915
Redemption of operating partnership units for common stock, shares	165,252
Net income	$ 61,406
Balance at Sep. 30, 2018	917,176	$ 440	709,488	(38,229)	671,699	245,477
Balance, shares at Sep. 30, 2018		43,962,167
Balance at Mar. 31, 2018	903,586	$ 440	709,461	(47,854)	662,047	241,539
Balance, shares at Mar. 31, 2018		43,960,884
Dividends and distributions	(15,176)			(10,990)	(10,990)	(4,186)
Redemption of operating partnership units for common stock			27		27	(27)
Redemption of operating partnership units for common stock, shares		1,283
Net income	23,936			17,334	17,334	6,602
Equity based compensation	180					180
Balance at Jun. 30, 2018	912,526	$ 440	709,488	(41,510)	668,418	244,108
Balance, shares at Jun. 30, 2018		43,962,167
Dividends and distributions	(15,176)			(10,990)	(10,990)	(4,186)
Net income	19,706			14,271	14,271	5,435
Equity based compensation	120					120
Balance at Sep. 30, 2018	$ 917,176	$ 440	$ 709,488	$ (38,229)	$ 671,699	$ 245,477
Balance, shares at Sep. 30, 2018		43,962,167

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income	$ 61,406	$ 42,384
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	35,632	38,997
Amortization of deferred financing costs	2,568	3,101
Allowance for funds used during construction - other funds	(1,094)	(318)
Equity based compensation	440	428
Changes in assets and liabilities:
Due from affiliates	1,624	4,036
Inventory	(833)	95
Prepaids and other current assets	(66)	(27)
Accounts payable and accrued liabilities	(590)	334
Net cash provided by operating activities	99,087	89,030
Cash flows from investing activities
Additions to electric plant	(48,653)	(147,803)
Proceeds from asset exchange transaction	1,632
Net cash used in investing activities	(47,021)	(147,803)
Cash flows from financing activities
Proceeds from short-term borrowings	118,000	110,500
Repayments of short-term borrowings	(58,000)	(213,000)
Proceeds from borrowings of long-term debt		200,000
Repayments of long-term debt	(66,185)	(5,845)
Deferred financing costs		(809)
Dividends and distributions paid	(45,521)	(45,499)
Net cash (used in) provided by financing activities	(51,706)	45,347
Net increase (decrease) in cash, cash equivalents and restricted cash	360	(13,426)
Cash, cash equivalents and restricted cash at beginning of period	4,550	19,294
Cash, cash equivalents and restricted cash at end of period	$ 4,910	$ 5,868

Description of Business and Pre

Description of Business and Presentation of Financial Statements	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business and Presentation of Financial Statements	1. Description of Business and Presentation of Financial Statements Basis of Presentation InfraREIT, Inc. is a Maryland corporation, which may be referred to in these financial statements as the “Company,” “InfraREIT,” “we,” “us” and “our.” These unaudited interim consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. For further information, refer to the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2017 filed with the U.S. Securities and Exchange Commission (SEC) on March 5, 2018 (2017 Form 10-K). We held 72.4% of the outstanding partnership units (OP Units) in InfraREIT Partners, LP (Operating Partnership or InfraREIT LP) as of September 30, 2018 and are its general partner. We include the accounts of the Operating Partnership and its subsidiaries in our consolidated financial statements. Hunt Consolidated, Inc. (Hunt) affiliates, current or former employees and members of our board of directors held the other 27.6% of the outstanding OP Units as of September 30, 2018. Use of Estimates The preparation of our consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Recent Accounting Guidance Recently Adopted Accounting Guidance In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Clarification of Certain Cash Receipts and Cash Payments In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 203): Restricted Cash (A Consensus of the FASB Emerging Issues Task Force) Recent Accounting Guidance Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842 Leases (Topic 842): Targeted Improvements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement

2017 Asset Exchange Transaction

2017 Asset Exchange Transaction	9 Months Ended
	Sep. 30, 2018
Nonmonetary Transactions [Abstract]
2017 Asset Exchange Transaction	2 . 2017 Asset Exchange Transaction In July 2017, our regulated subsidiary, Sharyland Distribution & Transmission Services, L.L.C. (SDTS), and our sole tenant, Sharyland Utilities, L.P. (Sharyland), signed a definitive agreement (2017 Asset Exchange Agreement) with Oncor Electric Delivery Company LLC (Oncor) to exchange SDTS’s retail distribution assets and certain transmission assets for a group of Oncor’s transmission assets located in Northwest and Central Texas (2017 Asset Exchange Transaction). The 2017 Asset Exchange Transaction closed in November 2017 and, among other things, resulted in SDTS exchanging $403 million of net assets for $383 million of transmission assets owned by Oncor, $18 million of net cash and a $2 million receivable from Oncor as of December 31, 2017. The transaction resulted in a gain of $0.3 million for SDTS. The receivable from Oncor was included in prepaids and other current assets in the Consolidated Balance Sheets at December 31, 2017 and was collected during the first quarter of 2018. These transactions were structured to qualify, in part, as a simultaneous tax deferred like-kind exchange of assets to the extent that the assets are of “like kind” (within the meaning of Section 1031 of the Internal Revenue Code of 1986, as amended).

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash	9 Months Ended
	Sep. 30, 2018
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents and Restricted Cash	3 . Cash, Cash Equivalents and Restricted Cash The following table provides a reconciliation of cash, cash equivalents and restricted cash within the Consolidated Balance Sheets that sum to the total of the same such amounts shown on the Consolidated Statements of Cash Flows: September 30, (In thousands) 2018 2017 Cash and cash equivalents $ 3,223 $ 4,186 Restricted cash 1,687 1,682 Total cash, cash equivalents and restricted cash shown on the Statement of Cash Flows $ 4,910 $ 5,868 Amounts included in restricted cash represent the principal and interest payable for two consecutive periods associated with the $25.0 million senior secured notes of the Operating Partnership’s wholly-owned subsidiary, Transmission and Distribution Company, L.L.C. (TDC), as described in Note 9, Long-Term Debt

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	4 . Related Party Transactions We lease, through SDTS, all our regulated assets to Sharyland through several lease agreements. Under the leases, we have agreed to fund capital expenditures for footprint projects. Our leases define “footprint projects” to be transmission or, if applicable, distribution projects that (1) are primarily situated within our current or previous distribution service territory, as applicable, (2) physically hang from our existing transmission assets, such as the addition of another circuit to our existing transmission lines, or that are physically located within one of our substations or (3) connect or are otherwise added to transmission lines or other properties that comprise a part of the transmission assets acquired in the 2017 Asset Exchange Transaction. We earned lease revenue from Sharyland under these agreements of $48.9 million and $51.6 million during the three months ended September 30, 2018 and 2017, respectively. We earned lease revenue of $142.4 million and $131.7 million from Sharyland during the nine months ended September 30, 2018 and 2017, respectively. In connection with our leases with Sharyland, we had a deferred rent liability of $14.6 million and $14.7 million as of September 30, 2018 and December 31, 2017, respectively, which is included in accounts payable and accrued liabilities on the Consolidated Balance Sheets. In addition to rent payments that Sharyland makes to us, we and Sharyland also make payments to each other under the leases that primarily consist of payments to reimburse Sharyland for the costs of gross plant and equipment added to our regulated assets. For the nine months ended September 30, 2018 and 2017, the net amount of payments we made to Sharyland was $48.3 million and $151.2 million, respectively. In July 2017, SDTS and Sharyland entered into a letter agreement (Side Letter) in which they agreed to certain terms and conditions to address the actual or potential conflicts of interest arising between SDTS and Sharyland in connection with the 2017 Asset Exchange Transaction. Specifically, the Side Letter includes, among other things, certain representations and warranties from Sharyland that correspond to representations and warranties of SDTS under the 2017 Asset Exchange Agreement relating to certain matters for which SDTS relies, in whole or in part, upon Sharyland under the leases and as operator of the assets and an allocation of expenses incurred in connection with the transactions. For information related to the 2017 Asset Exchange Transaction, see Note 2, 2017 Asset Exchange Transaction As of September 30, 2018 and December 31, 2017, accounts payable and accrued liabilities on the Consolidated Balance Sheets included $5.0 million and $2.1 million, respectively, related to amounts owed to Sharyland for construction costs incurred and property taxes paid on our behalf. As of September 30, 2018 and December 31, 2017, amounts due from affiliates on the Consolidated Balance Sheets included $33.4 million and $35.2 million, respectively, related to amounts owed by Sharyland primarily associated with our leases. The management fee paid to Hunt Utility Services, LLC (Hunt Manager) for the nine months ended September 30, 2018 and 2017 was $10.3 million and $14.1 million, respectively. There were no prepaid or accrued amounts associated with the management fees on the Consolidated Balance Sheets as of September 30, 2018 and December 31, 2017. As of December 31, 2016, there was $3.5 million accrued associated with management fees on the Consolidated Balance Sheets. Additionally, during the nine months ended September 30, 2018 and 2017, we paid Hunt Manager $0.1 million and $0.2 million, respectively, for reimbursement of annual software license and maintenance fees and other expenses in accordance with our management agreement. Our management agreement with Hunt Manager provides for an annual base fee, or management fee. The base fee for each 12 month period beginning each April 1 will equal 1.50% of our total equity as of December 31 of the immediately preceding year, subject to a $30.0 million cap. The term of the management agreement expires December 31, 2019 and will automatically renew for successive five year terms unless a majority of our independent directors decides to terminate the agreement. The annual base fees through March 31, 2019 are as follows: (In millions) Base Fee April 1, 2016 - March 31, 2017 $ 14.0 April 1, 2017 - March 31, 2018 14.2 April 1, 2018 - March 31, 2019 13.5 For information related to the pending sale of InfraREIT and asset exchange with Sharyland, including the proposed termination of the leases and management agreement, see Note 20, Subsequent Events

Electric Plant and Depreciation

Electric Plant and Depreciation	9 Months Ended
	Sep. 30, 2018
Public Utilities Property Plant And Equipment [Abstract]
Electric Plant and Depreciation	5 . Electric Plant and Depreciation The major classes of electric plant are as follows: (In thousands) September 30, 2018 December 31, 2017 Electric plant: Transmission plant $ 1,784,175 $ 1,685,466 Distribution plant 151,458 143,865 General plant 3,023 3,023 Total plant in service 1,938,656 1,832,354 Construction work in progress 60,027 113,643 Total electric plant 1,998,683 1,945,997 Accumulated depreciation (198,166 ) (173,768 ) Electric plant, net $ 1,800,517 $ 1,772,229 General plant consists primarily of a warehouse, buildings and associated assets. Construction work in progress (CWIP) reflects the regulated asset projects in various stages of construction prior to being placed in service. The capitalized amounts of CWIP consist primarily of route development expenditures, labor and materials expenditures, right of way acquisitions, engineering services and legal fees. Electric plant, net includes plant acquisition adjustments of $28.6 million and $29.4 million as of September 30, 2018 and December 31, 2017, respectively.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	6 . Goodwill Goodwill represents the excess of costs of an acquired business over the fair value of the assets acquired, less liabilities assumed. We conduct an impairment test of goodwill at least annually. As of September 30, 2018 and December 31, 2017, $138.4 million was recorded as goodwill on the Consolidated Balance Sheets.

Other Assets

Other Assets	9 Months Ended
	Sep. 30, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Other Assets	7 . Other Assets Other assets are as follows: September 30, 2018 December 31, 2017 (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Deferred financing costs on undrawn revolver $ 967 $ (736 ) $ 231 $ 967 $ (591 ) $ 376 Other regulatory assets: Deferred financing costs 10,365 (5,137 ) 5,228 28,570 (20,944 ) 7,626 Deferred costs recoverable in future years 23,793 — 23,793 23,793 — 23,793 Other regulatory assets 34,158 (5,137 ) 29,021 52,363 (20,944 ) 31,419 Investments 2,519 — 2,519 2,519 — 2,519 Other assets $ 37,644 $ (5,873 ) $ 31,771 $ 55,849 $ (21,535 ) $ 34,314 Deferred financing costs on undrawn revolver consist of costs incurred in connection with the establishment of the InfraREIT LP revolving credit facility. See Note 8, Borrowings Under Credit Facilities Other regulatory assets consist of deferred financing costs within our regulated subsidiary, SDTS. The deferred financing costs primarily consist of debt issuance costs incurred in connection with the construction of SDTS’s regulated assets or the refinancing of related debt. These assets are classified as regulatory assets and amortized over the length of the related loan. These costs are recovered through rates established in rate cases. The $18.2 million gross deferred financing costs associated with our 2011 Notes (defined below) were fully amortized in June 2018 and removed from our Consolidated Balance Sheets when the 2011 Notes were repaid at maturity. See Note 9, Long-Term Debt Deferred costs recoverable in future years of $23.8 million as of September 30, 2018 and December 31, 2017 represent operating costs incurred from the inception of Sharyland through 2007. We have determined that these costs are probable of recovery through future rates based on orders of the Public Utility Commission of Texas (PUCT) in Sharyland’s prior rate cases and regulatory precedent. In connection with the acquisition of Cap Rock Holding Corporation, we received a participation in the National Rural Utilities Cooperative Finance Corporation. We account for this investment under the cost method of accounting. We believe that the investment is not impaired as of September 30, 2018 and December 31, 2017.

Borrowings Under Credit Facilit

Borrowings Under Credit Facilities	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Borrowings Under Credit Facilities	8 . Borrowings Under Credit Facilities InfraREIT LP Revolving Credit Facility In 2014, InfraREIT LP entered into a $75.0 million revolving credit facility, led by Bank of America, N.A., as administrative agent, with up to $15.0 million available for issuance of letters of credit and a maturity date of December 10, 2019. The revolving credit facility is secured by certain assets of InfraREIT LP, including accounts and other personal property, and is guaranteed by us and TDC, with the TDC guarantee secured by the assets of, and InfraREIT LP’s equity interests in, TDC on materially the same basis as TDC’s senior secured notes described below in Note 9, Long-Term Debt Borrowings and other extensions of credit under the revolving credit facility bear interest, at InfraREIT LP’s election, at a rate equal to (1) the one, two, three or six month London Interbank Offered Rate (LIBOR) plus 2.5%, or (2) a base rate (equal to the highest of (a) the Federal Funds Rate plus ½ of 1%, (b) the administrative agent’s prime rate and (c) LIBOR plus 1%) plus 1.5%. Letters of credit are subject to a letter of credit fee equal to the daily amount available to be drawn times 2.5%. InfraREIT LP is also required to pay a commitment fee and other customary fees under the revolving credit facility. InfraREIT LP may prepay amounts outstanding under the revolving credit facility in whole or in part without premium or penalty. As of September 30, 2018 and December 31, 2017, there were no borrowings or letters of credit outstanding and there was $75.0 million of borrowing capacity available under the revolving credit facility. As of September 30, 2018 and December 31, 2017, InfraREIT LP was in compliance with all debt covenants under the credit agreement. SDTS Revolving Credit Facility In 2014, SDTS entered into the third amended and restated credit agreement led by Royal Bank of Canada, as administrative agent, with a maturity date of December 10, 2019. The credit agreement contains a revolving credit facility with a borrowing capacity up to $250.0 million with up to $25.0 million of the revolving credit facility available for issuance of letters of credit and up to $5.0 million of the revolving credit facility available for swingline loans. The revolving credit facility is secured by certain of SDTS’s regulated assets, the leases, certain accounts and TDC’s equity interests in SDTS on the same basis as SDTS’s various senior secured note obligations described below in Note 9, Long-Term Debt The interest rate for the revolving credit facility is based, at SDTS’s option, at a rate equal to either (1) a base rate, determined as the greatest of (a) the administrative agent’s prime rate, (b) the federal funds effective rate plus ½ of 1% and (c) LIBOR plus 1.00% per annum, plus a margin of either 0.75% or 1.00% per annum, depending on the total debt to capitalization ratio of SDTS on a consolidated basis or (2) LIBOR plus a margin of either 1.75% or 2.00% per annum, depending on the total debt to capitalization ratio of SDTS on a consolidated basis. SDTS is also required to pay a commitment fee and other customary fees under its revolving credit facility. SDTS is entitled to prepay amounts outstanding under the revolving credit facility with no prepayment penalty. As of September 30, 2018, SDTS had $101.0 million of borrowings outstanding at a weighted average interest rate of 4.21%, no letters of credit outstanding and $149.0 million of borrowing capacity available under this revolving credit facility. As of December 31, 2017, SDTS had $41.0 million of borrowings outstanding at a weighted average interest rate of 3.12% with no letters of credit outstanding and $209.0 million of borrowing capacity available under this revolving credit facility. As of September 30, 2018 and December 31, 2017, SDTS was in compliance with all debt covenants under the credit agreement. The credit agreements require InfraREIT LP and SDTS to comply with customary covenants for facilities of this type, including: debt to capitalization ratios, debt service coverage ratios, limitations on additional debt, liens, investments, mergers, acquisitions, dispositions or entry into any line of business other than the business of the transmission and distribution of electric power and the provision of ancillary services and certain restrictions on the payment of dividends. The debt to capitalization ratio on the SDTS credit facility is calculated on a combined basis with Sharyland. The credit agreements also contain restrictions on the amount of Sharyland’s indebtedness and other restrictions on, and covenants applicable to, Sharyland. The revolving credit facilities of InfraREIT LP and SDTS are subject to customary events of default. If an event of default occurs under either facility and is continuing, the lenders may accelerate amounts due under such revolving credit facility.

Long-Term Debt

Long-Term Debt	9 Months Ended
	Sep. 30, 2018
Debt Instruments [Abstract]
Long-Term Debt	9 . Long-Term Debt Long-term debt consisted of the following: September 30, 2018 December 31, 2017 (Dollar amounts in thousands) Maturity Date Amount Outstanding Interest Rate Amount Outstanding Interest Rate TDC Senior secured notes - $25.0 million December 30, 2020 $ 15,313 8.50% $ 16,250 8.50% SDTS Senior secured notes - $60.0 million June 20, 2018 — n/a 60,000 5.04% Senior secured term loan - $200.0 million June 5, 2020 200,000 3.42% 200,000 2.71% Senior secured notes - $400.0 million December 3, 2025 400,000 3.86% 400,000 3.86% Senior secured notes - $100.0 million January 14, 2026 100,000 3.86% 100,000 3.86% Senior secured notes - $53.5 million December 30, 2029 38,905 7.25% 40,546 7.25% Senior secured notes - $110.0 million September 30, 2030 89,214 6.47% 92,821 6.47% Total SDTS debt 828,119 893,367 Total long-term debt 843,432 909,617 Less unamortized deferred financing costs (72 ) (97 ) Total long-term debt, less deferred financing costs 843,360 909,520 Less current portion of long-term debt (8,667 ) (68,305 ) Debt classified as long-term debt, less deferred financing costs $ 834,693 $ 841,215 In 2010, TDC issued $25.0 million aggregate principal amount of 8.50% per annum senior secured notes to The Prudential Insurance Company of America and affiliates (TDC Notes). Principal and interest on the TDC Notes are payable quarterly, and the TDC Notes are secured by the assets of, and InfraREIT LP’s equity interest in, TDC on materially the same basis as with lenders under InfraREIT LP’s revolving credit facility described above in Note 7, Borrowings Under Credit Facilities SDTS had $60.0 million aggregate principal amount of 5.04% per annum senior secured notes that were issued to The Prudential Insurance Company of America and affiliates in 2011 (2011 Notes). Interest was payable quarterly while no principal payments were due until maturity. These notes were paid in full at maturity during June 2018 with proceeds from SDTS’s revolving credit facility. In 2017, SDTS entered into a $200.0 million senior secured term loan credit facility (2017 Term Loan) with Canadian Imperial Bank of Commerce, New York Branch (CIBC) and Mizuho Bank, Ltd., as lenders, and CIBC as administrative agent. The interest rate for the 2017 Term Loan is based, at SDTS’s option, at a rate equal to either (1) a base rate, determined as the greatest of (a) the administrative agent’s prime rate, (b) the federal funds effective rate plus 0.5% and (c) LIBOR plus 1.00% per annum, plus a margin of 0.25% per annum or (2) LIBOR plus a margin of 1.25% per annum. The LIBOR interest period may be one, two, three or six months, but interest is payable no less frequently than quarterly. In 2015, SDTS issued $400.0 million series A senior secured notes (Series A Notes), and in 2016 issued an additional $100.0 million series B senior secured notes (Series B Notes). These senior secured notes are due at maturity and bear interest at a rate of 3.86% per annum, payable semi-annually. The outstanding accrued interest payable on the Series A Notes is due each June and December while the accrued interest payable on the Series B Notes is due each January and July. In 2009, SDTS issued $53.5 million aggregate principal amount of 7.25% per annum senior secured notes to The Prudential Insurance Company of America and affiliates (2009 Notes). Principal and interest on the 2009 Notes are payable quarterly. In 2010, SDTS issued $110.0 million aggregate principal amount of 6.47% per annum senior secured notes to The Prudential Insurance Company of America (2010 Notes). Principal and interest on the 2010 Notes are payable quarterly. SDTS and TDC are entitled to prepay amounts outstanding under their senior secured notes, subject to a prepayment penalty equal to the excess of the discounted value of the remaining scheduled payments with respect to such notes over the amount of the prepaid notes. SDTS is entitled to prepay amounts outstanding under the 2017 Term Loan with no prepayment penalty. The 2017 Term Loan is also subject to required prepayments upon the occurrence of certain events. The agreements governing the senior secured notes and 2017 Term Loan contain customary covenants, such as debt to capitalization ratios, debt service coverage ratios, limitations on liens, dispositions, mergers, entry into other lines of business, investments and the incurrence of additional indebtedness. The debt to capitalization ratios are calculated on a combined basis with Sharyland. SDTS’s Series A Notes and Series B Notes are not required to maintain a debt service coverage ratio. As of September 30, 2018 and December 31, 2017, SDTS and TDC were in compliance with all debt covenants under the applicable agreements. See Note 20, Subsequent Events SDTS’s Series A Notes, Series B Notes, 2009 Notes, 2010 Notes and 2017 Term Loan are, and the 2011 Notes were, secured by certain of SDTS’s regulated assets, the leases, certain accounts and TDC’s equity interests in SDTS on the same basis as SDTS’s revolving credit facility described above in Note 8, Borrowings Under Credit Facilities The senior secured notes of TDC and SDTS and 2017 Term Loan are subject to customary events of default. If an event of default occurs with respect to the notes and is continuing, the lenders may accelerate the applicable amounts due.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	10 . Fair Value of Financial Instruments The carrying amounts of our cash and cash equivalents, restricted cash, due from affiliates and accounts payable approximate fair value due to the short-term nature of these assets and liabilities. We had fixed interest rate borrowings totaling $643.4 million and $709.6 million under our senior secured notes with a weighted average interest rate of 4.5% and 4.6% per annum as of September 30, 2018 and December 31, 2017, respectively. The fair value of these borrowings was estimated using discounted cash flow analysis based on current market rates. As of September 30, 2018 and December 31, 2017, we had $200.0 million of borrowings under our 2017 Term Loan that accrues interest under a floating interest rate structure, which is typically repriced every month or three months. Accordingly, the carrying value of such indebtedness approximated its fair value for the amounts outstanding. Financial instruments, measured at fair value, by level within the fair value hierarchy were as follows: Carrying Fair Value (In thousands) Value Level 1 Level 2 Level 3 September 30, 2018 Long-term debt $ 843,432 $ — $ 859,303 $ — December 31, 2017 Long-term debt $ 909,617 $ — $ 950,522 $ —

Regulatory Matters

Regulatory Matters	9 Months Ended
	Sep. 30, 2018
Public Utilities Rate Matters [Abstract]
Regulatory Matters	1 1 . Regulatory Matters Regulatory Liability Regulatory liabilities are as follows: (In thousands) September 30, 2018 December 31, 2017 Cost of removal $ 56,032 $ 44,679 Excess ADFIT 55,779 55,779 Regulatory liabilities $ 111,811 $ 100,458 Our regulatory liability related to cost of removal is established through depreciation rates and represents amounts that we expect to incur in the future. The regulatory liability is recorded as a long-term liability net of actual removal costs incurred. As an owner of regulated utility assets, we established an accumulated deferred federal income tax (ADFIT) balance for regulatory purposes primarily associated with the difference between U.S. GAAP and federal income tax depreciation on our assets. This ADFIT was calculated based on a 35% corporate federal income tax rate but was not recorded on our consolidated balance sheets or income statements due to the expectation that we would not pay corporate federal income taxes as a result of our REIT structure. With the passage of the Tax Cuts and Jobs Act (TCJA), the corporate federal income tax rate was reduced to 21% effective for tax years beginning on or after January 1, 2018. Regulatory accounting rules require utilities to revalue their ADFIT balances based on a change in corporate federal income tax rates, to remove the difference from ADFIT and to create a regulatory liability for the reduction in ADFIT. Therefore, we reduced the ADFIT by $55.8 million and created a regulatory liability for regulatory purposes. Additionally, in accordance with Accounting Standards Codification (ASC) Topic 980, Regulated Operations Liabilities Rate Case Filing In January 2014, the PUCT approved a rate case (2013 Rate Case) filed by Sharyland applicable to our regulated assets providing for a capital structure consisting of 55% debt and 45% equity; a cost of debt of 6.73%; a return on equity of 9.70%; and a return on invested capital of 8.06% in calculating rates. The new rates became effective May 1, 2014. Under the order approving the 2013 Rate Case, Sharyland was required to file its next rate case in 2016 (2016 Rate Case). In November 2017, the 2016 Rate Case was dismissed resulting in the 2013 Rate Case regulatory parameters remaining in place. As part of the PUCT order approving the 2017 Asset Exchange Transaction, the PUCT also granted SDTS a CCN to continue to own and lease its assets to Sharyland. Under existing PUCT orders, SDTS and Sharyland are required to file a new rate case by July 1, 2020 using the test year ending December 31, 2019.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 2 . Commitments and Contingencies From time to time, we are a party to various legal proceedings arising in the ordinary course of business. Although we cannot predict the outcome of any such legal proceedings, we do not believe the resolution of these proceedings, individually or in the aggregate, will have a material impact on our business, financial condition or results of operations, liquidity or cash flows.

Equity

Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Equity	1 3 . Equity We and the Operating Partnership declared cash dividends on common stock and distributions on OP Units of $0.75 per share or unit, as applicable, during each of the nine months ended September 30, 2018 and 2017. We paid a total of $45.5 million in dividends and distributions during each of the nine months ended September 30, 2018 and 2017.

Noncontrolling Interest

Noncontrolling Interest	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Noncontrolling Interest	1 4 . Noncontrolling Interest We present as a noncontrolling interest the portion of any equity in entities that we control and consolidate but do not own. Generally, OP Units of our Operating Partnership participate in net income allocations and distributions and entitle their holder to the right, subject to the terms set forth in the partnership agreement, to require the Operating Partnership to redeem all or a portion of the OP Units held by such limited partner. At our option, we may satisfy this redemption requirement with cash or by exchanging shares of InfraREIT, Inc. common stock on a one-for-one basis. As of September 30, 2018 and December 31, 2017, there were a total of 16.7 million and 16.9 million OP Units, respectively, held by the limited partners of the Operating Partnership. During the nine months ended September 30, 2018 and 2017, an aggregate of 28,952 and 31,633 long-term incentive units (LTIP Units), respectively, were issued by the Operating Partnership to members of our board of directors. For additional information, refer to Note 17, Share-Based Compensation We follow the guidance issued by the FASB regarding the classification and measurement of redeemable securities. Accordingly, we have determined that the OP Units meet the requirements to be classified as permanent equity. During the nine months ended September 30, 2018, we redeemed 165,252 OP Units with the issuance of 165,252 shares of common stock. We redeemed 23,349 OP Units with the issuance of 23,349 shares of common stock during the nine months ended September 30, 2017.

Earnings Per Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	1 5 . Earnings Per Share Basic earnings per share is calculated by dividing net earnings after noncontrolling interest by the weighted average shares outstanding. Diluted earnings per share is calculated similarly, except that it includes the dilutive effect of the assumed redemption of OP Units for shares of our common stock, if such redemption were dilutive. The redemption of OP Units would have been anti-dilutive during the three and nine months ended September 30, 2018 and 2017. Earnings per share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Basic net income per share: Net income attributable to InfraREIT, Inc. $ 14,271 $ 15,330 $ 44,469 $ 30,587 Weighted average common shares outstanding 43,962 43,784 43,919 43,779 Basic net income per share $ 0.32 $ 0.35 $ 1.01 $ 0.70 Diluted net income per share: Net income attributable to InfraREIT, Inc. $ 14,271 $ 15,330 $ 44,469 $ 30,587 Weighted average common shares outstanding 43,962 43,784 43,919 43,779 Redemption of Operating Partnership units — — — — Weighted average dilutive shares outstanding 43,962 43,784 43,919 43,779 Diluted net income per share $ 0.32 $ 0.35 $ 1.01 $ 0.70 Due to the anti-dilutive effect, the computation of diluted earnings per share does not reflect the following adjustments: Net income attributable to noncontrolling interest $ 5,435 $ 5,908 $ 16,937 $ 11,797 Redemption of Operating Partnership units 16,742 16,891 16,785 16,896

Leases

Leases	9 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Leases	1 6 . Leases The following table shows the composition of our lease revenue: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2018 2017 2018 2017 Base rent (straight-line) $ 48,390 $ 42,336 $ 141,873 $ 122,382 Percentage rent 536 9,282 536 9,282 Total lease revenue $ 48,926 $ 51,618 $ 142,409 $ 131,664 SDTS has entered into various leases with Sharyland for all our placed in service regulated assets. The master lease agreements, as amended, expire at various dates from December 31, 2019 through December 31, 2022. Our leases primarily consist of base rent, but certain lease supplements contain percentage rent as well. The lease supplements governing the Stanton Transmission Loop, Permian Basin assets and assets acquired in the 2017 Asset Exchange Transaction, which are part of the competitive renewable energy zones (CREZ) assets, only provide for base rent. Rent for the assets in McAllen and the CREZ assets not acquired in the 2017 Asset Exchange Transaction is comprised primarily of base rent but also includes percentage rent. Prior to its termination on December 31, 2017, the lease that previously covered the Permian Basin assets as well as the assets in Brady and Celeste, Texas that were transferred to Oncor in the 2017 Asset Exchange Transaction also included a percentage rent component. Percentage rent under our leases is based on a percentage of Sharyland’s annual gross revenue, as defined in the applicable lease, in excess of annual specified breakpoints, which are at least equal to the base rent under each lease. The rate used for percentage rent for the reported time periods varies by lease and ranges from a high of 31% to a low of 23%. Because an annual specified breakpoint must be met under our leases before we can recognize any percentage rent, we anticipate that little to no percentage rent will be recognized in the first and second quarters of each year, with the largest amounts of percentage rent recognized during the third and fourth quarters of each year. See Note 20, Subsequent Events

Share Based Compensation

Share Based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	1 7 . Share-Based Compensation We currently utilize the InfraREIT, Inc. 2015 Equity Incentive Plan primarily for the annual compensation of the non-executive directors for their service on our board of directors. The following table shows the aggregate LTIP Units issued to members of our board of directors during the nine months ended September 30, 2018 and 2017: Grant Date LTIP Units Grant Date Fair Value per LTIP Unit Aggregate Fair Value (in thousands) Vesting Date January 2017 31,633 $ 18.02 $ 570 January 2018 January 2018 28,952 18.61 539 January 2019 As part of our board of directors’ quarterly compensation, each non-executive director can, subject to certain exceptions, elect to receive part of their compensation in our common stock instead of cash with full vesting upon issuance. During 2017 and 2018, all directors elected to receive their quarterly compensation in cash. The compensation expense, which represents the fair value of the stock or LTIP Unit measured at market price at the date of grant, is recognized on a straight-line basis over the vesting period. For each of the three months ended September 30, 2018 and 2017, $0.1 million was recognized as compensation expense related to these grants and is included in general and administrative expense on the Consolidated Statements of Operations. We recognized $0.4 million of compensation expense during each of the nine months ended September 30, 2018 and 2017. The unamortized compensation expense related to these grants was $0.1 million as of September 30, 2018.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	18. Income Taxes Historically, we have accrued for potential taxes, penalties and interest related to Texas state franchise taxes on our rental income on our Consolidated Balance Sheets. However, during the second quarter of 2018, we reached a settlement with the state of Texas in which no franchise taxes were owed on lease revenue for all tax years through 2017. As a result, the accrued liability for these potential taxes of $4.9 million and penalties and interest of $0.7 million were removed from our Consolidated Balance Sheets and recognized as an income tax benefit on our Consolidated Statements of Operations during the second quarter of 2018. The tax portion of the liability represented unrecognized tax benefits that, if recognized, would have impacted our effective tax rate. A reconciliation of the beginning and ending amount of unrecognized tax benefits follows: (In thousands) September 30, 2018 December 31, 2017 Balance at beginning of period $ 4,864 $ 3,827 Additions based on tax positions related to the current year — 1,037 Settlements (4,864 ) — Balance at end of period $ — $ 4,864 As a result of the Texas franchise tax settlement, we began accruing and paying Texas franchise tax on our gross lease revenues effective January 1, 2018.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	1 9 . Supplemental Cash Flow Information Supplemental cash flow information and non-cash investing and financing activities are as follows: Nine Months Ended September 30, (In thousands) 2018 2017 Supplemental cash flow information Cash paid for interest $ 28,317 $ 26,004 Non-cash investing and financing activities Change in accrued additions to electric plant (2,943 ) 8,901 Allowance for funds used during construction - debt 1,971 2,261 Redemption of operating partnership units for common stock 3,133 492 Dividends and distributions payable 15,176 15,169

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	20. Subsequent Events Pending Corporate Transactions Sale and Asset Exchange On October 18, 2018, InfraREIT and InfraREIT LP entered into a definitive agreement to be acquired by Oncor for $21.00 per share or OP Unit, as applicable, in cash, valued at approximately $1.275 billion, plus the assumption of our net debt of approximately $940 million as of September 30, 2018. As a condition to Oncor’s acquisition of InfraREIT, SDTS and Oncor also signed a definitive agreement with Sharyland to exchange, immediately prior to Oncor’s acquisition, SDTS’s South Texas assets for Sharyland’s Golden Spread Electric Cooperative interconnection located in the Texas Panhandle, along with certain development projects in the Texas Panhandle and South Plains regions, including the Lubbock Power & Light interconnection. The difference between the net book value of the exchanged assets will be paid in cash at closing. SDTS and Sharyland have agreed to terminate their existing leases in connection with the asset exchange. The asset exchange with Sharyland and merger with Oncor are mutually dependent on one another and neither will become effective without the closing of the other. Arrangements with Hunt Under our management agreement with Hunt Manager, which will be terminated upon the closing of the transactions, Hunt Manager is entitled to the payment of a termination fee upon the termination or non-renewal of the management agreement. The termination of the management agreement automatically triggers the termination of the development agreement between us and Hunt. We have agreed to pay Hunt approximately $40.5 million at the closing of the transactions to terminate the management agreement, development agreement, leases with Sharyland, and all other existing agreements between InfraREIT or our subsidiaries and Hunt, Sharyland or their affiliates. This amount is consistent with the termination fee that is contractually required under the management agreement. Closing Conditions The closing of the transactions is dependent upon and will be subject to several closing conditions, including: PUCT approval of the transactions; other regulatory approvals; stockholder approval; certain lender consents; the substantially concurrent closing of the acquisition by an affiliate of Sempra Energy of a 50% limited partnership interest in Sharyland Holdings, LP, which will own a 100% interest in Sharyland; and other customary closing conditions. Timeline Under the definitive agreements, SDTS, Sharyland and Oncor are required to file a Sale-Transfer-Merger application with the PUCT no later than November 30, 2018. A special meeting of our stockholders will be held following the filing of the definitive proxy statement with the SEC and subsequent mailing to our stockholders, which is expected to be filed by December 10, 2018. The transactions are expected to close by mid-2019.

Description of Business and P_2

Description of Business and Presentation of Financial Statements (Policies)	9 Months Ended
	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation InfraREIT, Inc. is a Maryland corporation, which may be referred to in these financial statements as the “Company,” “InfraREIT,” “we,” “us” and “our.” These unaudited interim consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the nine months ended September 30, 2018 are not necessarily indicative of the results that may be expected for the year ending December 31, 2018. For further information, refer to the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2017 filed with the U.S. Securities and Exchange Commission (SEC) on March 5, 2018 (2017 Form 10-K). We held 72.4% of the outstanding partnership units (OP Units) in InfraREIT Partners, LP (Operating Partnership or InfraREIT LP) as of September 30, 2018 and are its general partner. We include the accounts of the Operating Partnership and its subsidiaries in our consolidated financial statements. Hunt Consolidated, Inc. (Hunt) affiliates, current or former employees and members of our board of directors held the other 27.6% of the outstanding OP Units as of September 30, 2018.
Use of Estimates	Use of Estimates The preparation of our consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates.
Recent Accounting Guidance	Recent Accounting Guidance Recently Adopted Accounting Guidance In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2014-09, Revenue from Contracts with Customers In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Clarification of Certain Cash Receipts and Cash Payments In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 203): Restricted Cash (A Consensus of the FASB Emerging Issues Task Force) Recent Accounting Guidance Not Yet Adopted In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842 Leases (Topic 842): Targeted Improvements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash (Tables)	9 Months Ended
	Sep. 30, 2018
Cash And Cash Equivalents [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash within Consolidated Balance Sheets	The following table provides a reconciliation of cash, cash equivalents and restricted cash within the Consolidated Balance Sheets that sum to the total of the same such amounts shown on the Consolidated Statements of Cash Flows: September 30, (In thousands) 2018 2017 Cash and cash equivalents $ 3,223 $ 4,186 Restricted cash 1,687 1,682 Total cash, cash equivalents and restricted cash shown on the Statement of Cash Flows $ 4,910 $ 5,868

Related Party Transactions (Tab

Related Party Transactions (Tables)	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Schedule of Annual Base Fees	The annual base fees through March 31, 2019 are as follows: (In millions) Base Fee April 1, 2016 - March 31, 2017 $ 14.0 April 1, 2017 - March 31, 2018 14.2 April 1, 2018 - March 31, 2019 13.5

Electric Plant and Depreciati_2

Electric Plant and Depreciation (Tables)	9 Months Ended
	Sep. 30, 2018
Public Utilities Property Plant And Equipment [Abstract]
Schedule of Major Classes of Electric Plant	The major classes of electric plant are as follows: (In thousands) September 30, 2018 December 31, 2017 Electric plant: Transmission plant $ 1,784,175 $ 1,685,466 Distribution plant 151,458 143,865 General plant 3,023 3,023 Total plant in service 1,938,656 1,832,354 Construction work in progress 60,027 113,643 Total electric plant 1,998,683 1,945,997 Accumulated depreciation (198,166 ) (173,768 ) Electric plant, net $ 1,800,517 $ 1,772,229

Other Assets (Tables)

Other Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Summary of Other Assets	Other assets are as follows: September 30, 2018 December 31, 2017 (In thousands) Gross Carrying Amount Accumulated Amortization Net Carrying Amount Gross Carrying Amount Accumulated Amortization Net Carrying Amount Deferred financing costs on undrawn revolver $ 967 $ (736 ) $ 231 $ 967 $ (591 ) $ 376 Other regulatory assets: Deferred financing costs 10,365 (5,137 ) 5,228 28,570 (20,944 ) 7,626 Deferred costs recoverable in future years 23,793 — 23,793 23,793 — 23,793 Other regulatory assets 34,158 (5,137 ) 29,021 52,363 (20,944 ) 31,419 Investments 2,519 — 2,519 2,519 — 2,519 Other assets $ 37,644 $ (5,873 ) $ 31,771 $ 55,849 $ (21,535 ) $ 34,314

Long-Term Debt (Tables)

Long-Term Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Instruments [Abstract]
Components of Long-Term Debt	Long-term debt consisted of the following: September 30, 2018 December 31, 2017 (Dollar amounts in thousands) Maturity Date Amount Outstanding Interest Rate Amount Outstanding Interest Rate TDC Senior secured notes - $25.0 million December 30, 2020 $ 15,313 8.50% $ 16,250 8.50% SDTS Senior secured notes - $60.0 million June 20, 2018 — n/a 60,000 5.04% Senior secured term loan - $200.0 million June 5, 2020 200,000 3.42% 200,000 2.71% Senior secured notes - $400.0 million December 3, 2025 400,000 3.86% 400,000 3.86% Senior secured notes - $100.0 million January 14, 2026 100,000 3.86% 100,000 3.86% Senior secured notes - $53.5 million December 30, 2029 38,905 7.25% 40,546 7.25% Senior secured notes - $110.0 million September 30, 2030 89,214 6.47% 92,821 6.47% Total SDTS debt 828,119 893,367 Total long-term debt 843,432 909,617 Less unamortized deferred financing costs (72 ) (97 ) Total long-term debt, less deferred financing costs 843,360 909,520 Less current portion of long-term debt (8,667 ) (68,305 ) Debt classified as long-term debt, less deferred financing costs $ 834,693 $ 841,215

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Financial Instruments Measured at Fair Value	Financial instruments, measured at fair value, by level within the fair value hierarchy were as follows: Carrying Fair Value (In thousands) Value Level 1 Level 2 Level 3 September 30, 2018 Long-term debt $ 843,432 $ — $ 859,303 $ — December 31, 2017 Long-term debt $ 909,617 $ — $ 950,522 $ —

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2018
Public Utilities Rate Matters [Abstract]
Summary of Regulatory Liabilities	Regulatory liabilities are as follows: (In thousands) September 30, 2018 December 31, 2017 Cost of removal $ 56,032 $ 44,679 Excess ADFIT 55,779 55,779 Regulatory liabilities $ 111,811 $ 100,458

Earnings Per Share (Tables)

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Computation of Earnings Per Share	Earnings per share are calculated as follows: Three Months Ended September 30, Nine Months Ended September 30, (In thousands, except per share data) 2018 2017 2018 2017 Basic net income per share: Net income attributable to InfraREIT, Inc. $ 14,271 $ 15,330 $ 44,469 $ 30,587 Weighted average common shares outstanding 43,962 43,784 43,919 43,779 Basic net income per share $ 0.32 $ 0.35 $ 1.01 $ 0.70 Diluted net income per share: Net income attributable to InfraREIT, Inc. $ 14,271 $ 15,330 $ 44,469 $ 30,587 Weighted average common shares outstanding 43,962 43,784 43,919 43,779 Redemption of Operating Partnership units — — — — Weighted average dilutive shares outstanding 43,962 43,784 43,919 43,779 Diluted net income per share $ 0.32 $ 0.35 $ 1.01 $ 0.70 Due to the anti-dilutive effect, the computation of diluted earnings per share does not reflect the following adjustments: Net income attributable to noncontrolling interest $ 5,435 $ 5,908 $ 16,937 $ 11,797 Redemption of Operating Partnership units 16,742 16,891 16,785 16,896

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2018
Leases [Abstract]
Schedule of Composition of Lease Revenue	The following table shows the composition of our lease revenue: Three Months Ended September 30, Nine Months Ended September 30, (In thousands) 2018 2017 2018 2017 Base rent (straight-line) $ 48,390 $ 42,336 $ 141,873 $ 122,382 Percentage rent 536 9,282 536 9,282 Total lease revenue $ 48,926 $ 51,618 $ 142,409 $ 131,664

Share-Based Compensation (Table

Share-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Aggregate LTIP Units Issued to Board of Directors	The following table shows the aggregate LTIP Units issued to members of our board of directors during the nine months ended September 30, 2018 and 2017: Grant Date LTIP Units Grant Date Fair Value per LTIP Unit Aggregate Fair Value (in thousands) Vesting Date January 2017 31,633 $ 18.02 $ 570 January 2018 January 2018 28,952 18.61 539 January 2019

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits	The tax portion of the liability represented unrecognized tax benefits that, if recognized, would have impacted our effective tax rate. A reconciliation of the beginning and ending amount of unrecognized tax benefits follows: (In thousands) September 30, 2018 December 31, 2017 Balance at beginning of period $ 4,864 $ 3,827 Additions based on tax positions related to the current year — 1,037 Settlements (4,864 ) — Balance at end of period $ — $ 4,864

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information and Non-cash Investing and Financing Activities	Supplemental cash flow information and non-cash investing and financing activities are as follows: Nine Months Ended September 30, (In thousands) 2018 2017 Supplemental cash flow information Cash paid for interest $ 28,317 $ 26,004 Non-cash investing and financing activities Change in accrued additions to electric plant (2,943 ) 8,901 Allowance for funds used during construction - debt 1,971 2,261 Redemption of operating partnership units for common stock 3,133 492 Dividends and distributions payable 15,176 15,169

Description of Business and P_3

Description of Business and Presentation of Financial Statements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018
Description Of Business And Presentation Of Financial Statements [Line Items]
Percentage of partnership units outstanding	72.40%
Hunt Consolidated, Inc.
Description Of Business And Presentation Of Financial Statements [Line Items]
Percentage of partnership units outstanding	27.60%

2017 Asset Exchange Transacti_2

2017 Asset Exchange Transaction - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Nonmonetary Transaction [Line Items]
Proceeds from asset exchange transaction	$ 1,632
Sharyland Distribution & Transmission Services, L.L.C. | 2017 Asset Exchange Agreement | Oncor Electric Delivery Company LLC
Nonmonetary Transaction [Line Items]
Net assets exchanged		$ 403,000
Transmission assets		383,000
Proceeds from asset exchange transaction		18,000
Gain on asset exchange transaction		300
Sharyland Distribution & Transmission Services, L.L.C. | 2017 Asset Exchange Agreement | Oncor Electric Delivery Company LLC | Prepaids and Other Current Assets
Nonmonetary Transaction [Line Items]
Receivable under asset exchange transaction		$ 2,000

Cash, Cash Equivalents and Re_3

Cash, Cash Equivalents and Restricted Cash - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash within Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 3,223	$ 2,867	$ 4,186
Restricted cash	1,687	1,683	1,682
Total cash, cash equivalents and restricted cash shown on the Statement of Cash Flows	$ 4,910	$ 4,550	$ 5,868	$ 19,294

Cash, Cash Equivalents and Re_4

Cash, Cash Equivalents and Restricted Cash - Additional Information (Details) $ in Millions	Sep. 30, 2018USD ($)
Transmission and Distribution Company, L.L.C | Senior Secured Notes, 8.50%
Restricted Cash And Cash Equivalents Items [Line Items]
Long-term debt, face amount	$ 25

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Due from affiliates	$ 33,401,000		$ 33,401,000		$ 35,172,000
Hunt Utility Services, LLC
Related Party Transaction [Line Items]
Payment for management fee			10,300,000	$ 14,100,000
Prepaid management fee	0		0		0
Accrued management fee	$ 0		$ 0		0	$ 3,500,000
Management agreement expiration date			Dec. 31, 2019
Agreement successive renewal terms			5 years
Management fee, description			The base fee for each 12 month period beginning each April 1 will equal 1.50% of our total equity as of December 31 of the immediately preceding year, subject to a $30.0 million cap
Investment management fee equity multiplier	1.50%		1.50%
Management fee cap	$ 30,000,000		$ 30,000,000
Hunt Utility Services, LLC | License and Maintenence Fees
Related Party Transaction [Line Items]
Reimbursement of annual software license and maintenance fees and other expenses			100,000	200,000
Sharyland
Related Party Transaction [Line Items]
Lease revenue from related party	48,900,000	$ 51,600,000	142,400,000	131,700,000
Deferred rent liability	14,600,000		14,600,000		14,700,000
Payments to acquire plant, and equipment			48,300,000	$ 151,200,000
Accounts payable and accrued liabilities	5,000,000		5,000,000		2,100,000
Due from affiliates	$ 33,400,000		$ 33,400,000		$ 35,200,000

Related Party Transactions - Sc

Related Party Transactions - Schedule of Annual Base Fees (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Related Party Transaction [Line Items]
Annual base fees		$ 14.2	$ 14
Scenario, Forecast
Related Party Transaction [Line Items]
Annual base fees	$ 13.5

Electric Plant and Depreciati_3

Electric Plant and Depreciation - Schedule of Major Classes of Electric Plant (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Electric plant:
Transmission plant	$ 1,784,175	$ 1,685,466
Distribution plant	151,458	143,865
General plant	3,023	3,023
Total plant in service	1,938,656	1,832,354
Construction work in progress	60,027	113,643
Total electric plant	1,998,683	1,945,997
Accumulated depreciation	(198,166)	(173,768)
Electric plant, net	$ 1,800,517	$ 1,772,229

Electric Plant and Depreciati_4

Electric Plant and Depreciation - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Public Utilities Property Plant And Equipment [Abstract]
Electric plant, net includes plant acquisition adjustments	$ 28.6	$ 29.4

Goodwill (Details)

Goodwill (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill	$ 138,384	$ 138,384

Other Assets - Summary of Other

Other Assets - Summary of Other Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Assets Noncurrent [Abstract]
Deferred financing costs on undrawn revolver, Gross Carrying Amount	$ 967	$ 967
Other regulatory assets Deferred financing costs, Gross Carrying Amount	10,365	28,570
Other regulatory assets Deferred costs recoverable in future years, Gross Carrying Amount	23,793	23,793
Other regulatory assets, Gross Carrying Amount	34,158	52,363
Investments, Gross Carrying Amount	2,519	2,519
Other assets, Gross Carrying Amount	37,644	55,849
Deferred financing costs on undrawn revolver, Accumulated Amortization	(736)	(591)
Other regulatory assets Deferred financing costs, Accumulated Amortization	(5,137)	(20,944)
Other regulatory assets, Accumulated Amortization	(5,137)	(20,944)
Other assets, Accumulated Amortization	(5,873)	(21,535)
Deferred financing costs on undrawn revolver, Net Carrying Amount	231	376
Other regulatory assets Deferred financing costs, Net Carrying Amount	5,228	7,626
Other regulatory assets Deferred costs recoverable in future years, Net Carrying Amount	23,793	23,793
Other regulatory assets, Net Carrying Amount	29,021	31,419
Investments, Net Carrying Amount	2,519	2,519
Other assets, Net Carrying Amount	$ 31,771	$ 34,314

Other Assets - Additional Infor

Other Assets - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Other Assets [Line Items]
Other regulatory assets Deferred financing costs, Gross Carrying Amount	$ 10,365,000	$ 28,570,000
Deferred costs recoverable in future years	23,793,000	23,793,000
Investment impaired	0	$ 0
Senior Secured Notes, 5.04%
Other Assets [Line Items]
Other regulatory assets Deferred financing costs, Gross Carrying Amount	$ 18,200,000

Borrowings Under Credit Facil_2

Borrowings Under Credit Facilities - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2014	Dec. 31, 2017
InfraREIT LP Revolving Credit Facility
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 75,000,000
Credit facility, maturity date		Dec. 10, 2019
Revolving credit facility, interest rate description	a rate equal to (1) the one, two, three or six month London Interbank Offered Rate (LIBOR) plus 2.5%, or (2) a base rate (equal to the highest of (a) the Federal Funds Rate plus ½ of 1%, (b) the administrative agent’s prime rate and (c) LIBOR plus 1%) plus 1.5%. Letters of credit are subject to a letter of credit fee equal to the daily amount available to be drawn times 2.5%.
Letter of credit fee multiplier		2.50%
Amount of revolving credit facility under agreement	$ 0		$ 0
Letters of credit outstanding amount	0		0
Line of credit facility, remaining borrowing capacity	$ 75,000,000		75,000,000
InfraREIT LP Revolving Credit Facility | One, Two, Three or Six Month London Interbank Offered Rate (LIBOR)
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		2.50%
InfraREIT LP Revolving Credit Facility | Federal Funds Rate
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		0.50%
InfraREIT LP Revolving Credit Facility | LIBOR
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		1.00%
InfraREIT LP Revolving Credit Facility | Base Rate
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		1.50%
InfraREIT LP Revolving Credit Facility | Letter Of Credit
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 15,000,000
Third Amended and Restated Credit Agreement | SDTS
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 250,000,000
Credit facility, maturity date		Dec. 10, 2019
Third Amended and Restated Credit Agreement | Letter Of Credit | SDTS
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 25,000,000
Third Amended and Restated Credit Agreement | Swingline Loans | SDTS
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity		$ 5,000,000
Revolving Credit Facility | SDTS
Line Of Credit Facility [Line Items]
Revolving credit facility, interest rate description	a rate equal to either (1) a base rate, determined as the greatest of (a) the administrative agent’s prime rate, (b) the federal funds effective rate plus ½ of 1% and (c) LIBOR plus 1.00% per annum, plus a margin of either 0.75% or 1.00% per annum, depending on the total debt to capitalization ratio of SDTS on a consolidated basis or (2) LIBOR plus a margin of either 1.75% or 2.00% per annum
Amount of revolving credit facility under agreement	$ 101,000,000		41,000,000
Line of credit facility, remaining borrowing capacity	$ 149,000,000		$ 209,000,000
Debt, weighted average interest rate	4.21%		3.12%
Revolving Credit Facility | Federal Funds Rate | SDTS
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		0.50%
Revolving Credit Facility | LIBOR | SDTS
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Revolving Credit Facility | LIBOR | SDTS | Minimum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		1.75%
Revolving Credit Facility | LIBOR | SDTS | Maximum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		2.00%
Revolving Credit Facility | Base Rate | SDTS | Minimum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		0.75%
Revolving Credit Facility | Base Rate | SDTS | Maximum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate		1.00%
Revolving Credit Facility | Letter Of Credit | SDTS
Line Of Credit Facility [Line Items]
Amount of revolving credit facility under agreement	$ 0		$ 0

Long-Term Debt - Components of

Long-Term Debt - Components of Long-Term Debt (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Long-term debt, Amount Outstanding	$ 843,432	$ 909,617
Less unamortized deferred financing costs	(72)	(97)
Total long-term debt, less deferred financing costs	843,360	909,520
Less current portion of long-term debt	(8,667)	(68,305)
Debt classified as long-term debt, less deferred financing costs	$ 834,693	$ 841,215
TDC | Senior Secured Notes, 8.50%
Debt Instrument [Line Items]
Long-term debt, Interest Rate	8.50%	8.50%		8.50%
Long-term debt, Amount Outstanding	$ 15,313	$ 16,250
Interest bearing note, maturity date	Dec. 30, 2020
SDTS
Debt Instrument [Line Items]
Long-term debt, Amount Outstanding	$ 828,119	$ 893,367
SDTS | Senior Secured Notes, 5.04%
Debt Instrument [Line Items]
Long-term debt, Interest Rate		5.04%	5.04%
Long-term debt, Amount Outstanding		$ 60,000
Interest bearing note, maturity date	Jun. 20, 2018
SDTS | Senior Secured Notes, 3.86%
Debt Instrument [Line Items]
Long-term debt, Interest Rate	3.86%	3.86%
Long-term debt, Amount Outstanding	$ 400,000	$ 400,000
Interest bearing note, maturity date	Dec. 3, 2025
SDTS | Senior Secured Notes, 3.86% Maturing in 2026
Debt Instrument [Line Items]
Long-term debt, Interest Rate	3.86%	3.86%
Long-term debt, Amount Outstanding	$ 100,000	$ 100,000
Interest bearing note, maturity date	Jan. 14, 2026
SDTS | Senior Secured Notes, 7.25%
Debt Instrument [Line Items]
Long-term debt, Interest Rate	7.25%	7.25%			7.25%
Long-term debt, Amount Outstanding	$ 38,905	$ 40,546
Interest bearing note, maturity date	Dec. 30, 2029
SDTS | Senior Secured Notes, 6.47%
Debt Instrument [Line Items]
Long-term debt, Interest Rate	6.47%	6.47%		6.47%
Long-term debt, Amount Outstanding	$ 89,214	$ 92,821
Interest bearing note, maturity date	Sep. 30, 2030
SDTS | Senior Secured Term Loan
Debt Instrument [Line Items]
Long-term debt, Amount Outstanding	$ 200,000	$ 200,000
Interest bearing note, maturity date	Jun. 5, 2020
Long-term debt, Interest Rate	3.42%	2.71%

Long-Term Debt - Components o_2

Long-Term Debt - Components of Long-Term Debt (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
TDC | Senior Secured Notes, 8.50%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 25		$ 25
SDTS | Senior Secured Notes, 5.04%
Debt Instrument [Line Items]
Long-term debt, face amount	60	$ 60
SDTS | Senior Secured Term Loan
Debt Instrument [Line Items]
Long-term debt, face amount	200
SDTS | Senior Secured Notes, 3.86%
Debt Instrument [Line Items]
Long-term debt, face amount	400
SDTS | Senior Secured Notes, 3.86% Maturing in 2026
Debt Instrument [Line Items]
Long-term debt, face amount	100
SDTS | Senior Secured Notes, 7.25%
Debt Instrument [Line Items]
Long-term debt, face amount	53.5			$ 53.5
SDTS | Senior Secured Notes, 6.47%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 110		$ 110

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Deferred financing costs, Net Carrying Amount	$ 231	$ 376
2017 Term Loan
Debt Instrument [Line Items]
Long-term debt, face amount	200,000	$ 200,000
TDC | Senior Secured Notes, 8.50%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 25,000					$ 25,000
Long-term debt, stated interest rate	8.50%	8.50%				8.50%
Deferred financing costs, Net Carrying Amount	$ 100	$ 100
SDTS | Senior Secured Notes, 5.04%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 60,000				$ 60,000
Long-term debt, stated interest rate		5.04%			5.04%
SDTS | 2017 Term Loan | Canadian Imperial Bank of Commerce, New York Branch and Mizuho Bank, Ltd.
Debt Instrument [Line Items]
Long-term debt, face amount		$ 200,000
Interest rate description	The interest rate for the 2017 Term Loan is based, at SDTS’s option, at a rate equal to either (1) a base rate, determined as the greatest of (a) the administrative agent’s prime rate, (b) the federal funds effective rate plus 0.5% and (c) LIBOR plus 1.00% per annum, plus a margin of 0.25% per annum or (2) LIBOR plus a margin of 1.25% per annum. The LIBOR interest period may be one, two, three or six months, but interest is payable no less frequently than quarterly.
SDTS | 2017 Term Loan | Canadian Imperial Bank of Commerce, New York Branch and Mizuho Bank, Ltd. | Federal Funds Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.50%
SDTS | 2017 Term Loan | Canadian Imperial Bank of Commerce, New York Branch and Mizuho Bank, Ltd. | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.00%
SDTS | 2017 Term Loan | Canadian Imperial Bank of Commerce, New York Branch and Mizuho Bank, Ltd. | Base Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		0.25%
SDTS | 2017 Term Loan | Canadian Imperial Bank of Commerce, New York Branch and Mizuho Bank, Ltd. | One, Two, Three or Six Month London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.25%
SDTS | Senior Secured Notes, 7.25%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 53,500						$ 53,500
Long-term debt, stated interest rate	7.25%	7.25%					7.25%
SDTS | Senior Secured Notes, 6.47%
Debt Instrument [Line Items]
Long-term debt, face amount	$ 110,000					$ 110,000
Long-term debt, stated interest rate	6.47%	6.47%				6.47%
SDTS Credit Agreements | Series A Notes
Debt Instrument [Line Items]
Long-term debt, face amount				$ 400,000
Long-term debt, stated interest rate				3.86%
SDTS Credit Agreements | Series B Notes
Debt Instrument [Line Items]
Long-term debt, face amount			$ 100,000
Long-term debt, stated interest rate			3.86%

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	$ 834,693	$ 841,215
2017 Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term debt, face amount	200,000	200,000
Senior Secured Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Long-term Debt	$ 643,400	$ 709,600
Debt, weighted average interest rate	4.50%	4.60%

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying Value
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt	$ 843,432	$ 909,617
Level 2 | Fair Value
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt	$ 859,303	$ 950,522

Regulatory Matters - Summary of

Regulatory Matters - Summary of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Public Utilities General Disclosures [Line Items]
Regulatory Liabilities	$ 111,811	$ 100,458
Cost of Removal
Public Utilities General Disclosures [Line Items]
Regulatory Liabilities	56,032	44,679
Excess ADFIT
Public Utilities General Disclosures [Line Items]
Regulatory Liabilities	$ 55,779	$ 55,779

Regulatory Matters - Additional

Regulatory Matters - Additional Information (Details) - USD ($) $ in Thousands	May 01, 2014	Sep. 30, 2018	Dec. 31, 2017
Public Utilities General Disclosures [Line Items]
Corporate federal income tax rate		21.00%	35.00%
Regulatory liability related to creation of excess accumulated deferred federal income tax		$ 55,800
Regulatory liabilities		111,811	$ 100,458
Sharyland
Public Utilities General Disclosures [Line Items]
Public utilities, approved capital structure, debt percentage	55.00%
Public utilities, approved capital structure, equity percentage	45.00%
Public utilities, approved cost of debt percentage	6.73%
Public utilities, approved return on equity, percentage	9.70%
Public utilities, approved return on invested capital, percentage	8.06%
Excess ADFIT
Public Utilities General Disclosures [Line Items]
Regulatory liabilities		$ 55,779	$ 55,779

Equity - Additional Information

Equity - Additional Information (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
Equity [Abstract]
Cash dividends declared per share to shareholders	$ 0.25	$ 0.25	$ 0.75	$ 0.75
Cash distributions declared to unit holders, per unit			$ 0.75	$ 0.75
Dividends and distributions paid			$ 45,521	$ 45,499

Noncontrolling Interest - Addit

Noncontrolling Interest - Additional Information (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Minority Interest [Line Items]
Description of units redeemed for cash or, at option, exchanged for common shares	one-for-one basis
OP Units held by the limited partners	16,700,000		16,900,000
Operating partnership units redeem	165,252	23,349
Common shares issued	165,252	23,349
LTIP Units
Minority Interest [Line Items]
Operating partnership units issued	28,952	31,633

Earnings Per Share - Computatio

Earnings Per Share - Computation of Earnings Per 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
Basic net income per share:
Net income attributable to InfraREIT, Inc.	$ 14,271	$ 15,330	$ 44,469	$ 30,587
Weighted average common shares outstanding	43,962	43,784	43,919	43,779
Basic net income per share	$ 0.32	$ 0.35	$ 1.01	$ 0.70
Diluted net income per share:
Net income attributable to InfraREIT, Inc.	$ 14,271	$ 15,330	$ 44,469	$ 30,587
Weighted average common shares outstanding	43,962	43,784	43,919	43,779
Weighted average dilutive shares outstanding	43,962	43,784	43,919	43,779
Diluted net income per share	$ 0.32	$ 0.35	$ 1.01	$ 0.70
Due to the anti-dilutive effect, the computation of diluted earnings per share does not reflect the following adjustments:
Net income attributable to noncontrolling interest	$ 5,435	$ 5,908	$ 16,937	$ 11,797
Redemption of Operating Partnership units	16,742	16,891	16,785	16,896

Leases - Schedule of Compositio

Leases - Schedule of Composition of Lease Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Leases [Abstract]
Base rent (straight-line)	$ 48,390	$ 42,336	$ 141,873	$ 122,382
Percentage rent	536	9,282	536	9,282
Total lease revenue	$ 48,926	$ 51,618	$ 142,409	$ 131,664

Leases - Additional Information

Leases - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018
Operating Leased Assets [Line Items]
Operating leases placed in services dates description	SDTS has entered into various leases with Sharyland for all our placed in service regulated assets. The master lease agreements, as amended, expire at various dates from December 31, 2019 through December 31, 2022.
Lease expiration date range, start date	Dec. 31, 2019
Lease expiration date range, end date	Dec. 31, 2022
S/B/C Lease
Operating Leased Assets [Line Items]
Lease terminated date	Dec. 31, 2017
Maximum
Operating Leased Assets [Line Items]
Rate of rent used, Percentage	31.00%
Minimum
Operating Leased Assets [Line Items]
Rate of rent used, Percentage	23.00%

Share-Based Compensation - Aggr

Share-Based Compensation - Aggregate LTIP Units Issued to Board of Directors (Details) - 2015 Equity Incentive Plan - Director - LTIP Units - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Grant Date	2018-01	2017-01
LTIP Units	28,952	31,633
Grant Date Fair Value per Share	$ 18.61	$ 18.02
Aggregate Fair Value	$ 539	$ 570
Vesting Date	2019-01	2018-01

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Details) - 2015 Equity Incentive Plan - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Unamortized stock compensation expense	$ 100,000		$ 100,000
General And Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Compensation expenses	$ 100,000	$ 100,000	$ 400,000	$ 400,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Accrued liability for potential taxes			$ 4,864
Texas
Income Tax Contingency [Line Items]
Franchise taxes on lease revenue		$ 0		$ 0
Accrued liability for potential taxes	$ 4,900
Penalties and interest	$ 700

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 4,864	$ 3,827
Additions based on tax positions related to the current year		1,037
Settlements	$ (4,864)
Balance at end of period		$ 4,864

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Supplemental Cash Flow Information and Non-cash Investing and Financing Activities (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Supplemental cash flow information
Cash paid for interest	$ 28,317	$ 26,004
Non-cash investing and financing activities
Change in accrued additions to electric plant	(2,943)	8,901
Allowance for funds used during construction - debt	1,971	2,261
Redemption of operating partnership units for common stock	3,133	492
Dividends and distributions payable	$ 15,176	$ 15,169	$ 15,169

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2018	Oct. 18, 2018
Sharyland Holdings, LP
Subsequent Event [Line Items]
Equity interest percentage	50.00%
Noncontrolling Interest, Ownership Percentage by Parent	100.00%
Hunt Consolidated, Inc.
Subsequent Event [Line Items]
Termination fee for termination agreement	$ 40.5
Oncor Electric Delivery Company LLC | Definitive Agreement
Subsequent Event [Line Items]
Business combination, assumption of net debt	$ 940
Subsequent Event | Oncor Electric Delivery Company LLC | Definitive Agreement
Subsequent Event [Line Items]
Business acquisition, share price		$ 21
Business acquisition, value in cash		$ 1,275