Additional Dividends

No definition available.

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- Definition

Awards Outstanding In Effect At Or Before Merger

+ References

No definition available.

+ Details

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Namespace Prefix:	itc_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

ESPP Additional Compensation Contributed by Employer

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

ESPP Aggregate Employee Contribution

+ References

No definition available.

+ Details

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- Definition

ESPP Employee Contribution

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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Period Type:	instant

- Definition

ESPP Employer Contribution

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
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- Definition

Merger consideration share-based compensation awards

+ References

No definition available.

+ Details

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Namespace Prefix:	itc_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e1043-128460

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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Balance Type:	na
Period Type:	duration

- Definition

Number of share instruments newly issued under a share-based compensation plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares issued which are neither cancelled nor held in the treasury.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

Name:	us-gaap_AwardTypeAxis=itc_ServiceBasedUnitsMember
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- Details

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- Details

Name:	itc_TypeOfOperatingCostAndExpenseAxis=itc_ExpenseRecognizedUponCompletionoftheMergerMember
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- Details

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- Details

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SHARE-BASED COMPENSATION (Details) - USD ($)	9 Months Ended	12 Months Ended
SHARE-BASED COMPENSATION (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Oct. 14, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards Outstanding In Effect At Or Before Merger		0
2017 Omnibus Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period	333,579
2017 Omnibus Plan \| Service-Based Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period	259,053
Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding	600,000
ESPP Aggregate Employee Contribution	10.00%
ESPP Additional Compensation Contributed by Employer	10.00%
Dividends	10.00%
Expense Recognized Upon Completion of the Merger
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Merger related expenses		$ 41,000,000
ITC Holdings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Merger consideration share-based compensation awards			$ 45.72
Minimum \| Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP Employee Contribution	1.00%
Maximum \| Employee Share Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP Employee Contribution	10.00%
ESPP Employer Contribution	1.00%