Letter of credit fee multiplier.

No definition available.

Name:	hifr_LetterOfCreditFeeMultiplier
Namespace Prefix:	hifr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the interest rate for the amounts borrowed under the credit facility, including the terms and the method for determining the interest rate (for example, fixed or variable, LIBOR plus a percentage, increasing rate, timing of interest rate resets, remarketing provisions).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateDescription
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_CreditFacilityAxis=hifr_InfraREITLPRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=hifr_OneTwoThreeOrSixMonthLondonInterbankOfferedRateLIBORMember
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Data Type:	na
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
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Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=hifr_ThirdAmendedAndRestatedCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	dei_LegalEntityAxis=hifr_SharylandDistributionAndTransmissionServicesLimitedLiabilityCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortTermDebtTypeAxis=hifr_SwinglineLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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Borrowings Under Credit Facilities - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
InfraREIT LP Revolving Credit Facility
Line Of Credit Facility [Line Items]
Amount of revolving credit facility under agreement	$ 0	$ 0	$ 75,000,000
Line of credit facility, remaining borrowing capacity	$ 75,000,000	75,000,000	15,000,000
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 Bank of America 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%
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%
Third Amended and Restated Credit Agreement \| SDTS Credit Agreements
Line Of Credit Facility [Line Items]
Credit facility, maturity date	Dec. 10, 2019
Credit facility, maximum borrowing capacity			250,000,000
Third Amended and Restated Credit Agreement \| SDTS Credit Agreements \| Letter Of Credit
Line Of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity			25,000,000
Third Amended and Restated Credit Agreement \| SDTS Credit Agreements \| Swingline Loans
Line Of Credit Facility [Line Items]
Line of credit facility, remaining borrowing capacity			$ 5,000,000
Revolving Credit Facility \| SDTS Credit Agreements
Line Of Credit Facility [Line Items]
Amount of revolving credit facility under agreement	$ 162,000,000	137,500,000
Line of credit facility, remaining borrowing capacity	$ 88,000,000	$ 112,500,000
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) the one, two, three or six month LIBOR plus a margin of either 1.75% or 2.00% per annum
Debt, weighted average interest rate	2.72%	2.50%
Revolving Credit Facility \| SDTS Credit Agreements \| Letter Of Credit
Line Of Credit Facility [Line Items]
Amount of revolving credit facility under agreement	$ 0	$ 0
Revolving Credit Facility \| One, Two, Three or Six Month London Interbank Offered Rate (LIBOR) \| SDTS Credit Agreements \| Minimum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.75%
Revolving Credit Facility \| One, Two, Three or Six Month London Interbank Offered Rate (LIBOR) \| SDTS Credit Agreements \| Maximum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Revolving Credit Facility \| Federal Funds Rate \| SDTS Credit Agreements
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.50%
Revolving Credit Facility \| LIBOR \| SDTS Credit Agreements
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.00%
Revolving Credit Facility \| Base Rate \| SDTS Credit Agreements \| Minimum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.75%
Revolving Credit Facility \| Base Rate \| SDTS Credit Agreements \| Maximum
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.00%