SEGMENT INFORMATION (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2015		Sep. 30, 2015	[1],[2]	Jun. 30, 2015	[1],[2]	Mar. 31, 2015	[1],[2]	Dec. 31, 2014		Sep. 30, 2014	[2]	Jun. 30, 2014	[2]	Mar. 31, 2014	[2]	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information
Operating revenues		$ 224,034	[1],[2]	$ 273,189		$ 275,058		$ 272,487		$ 231,097	[2]	$ 270,134		$ 263,214		$ 258,603		$ 1,044,768	[1],[2]	$ 1,023,048	[2]	$ 941,272
Depreciation and amortization																		144,672		128,036		118,596
Interest expense — net																		203,779		186,636		168,319
Income (loss) before income taxes																		383,877		394,405		352,368
Income tax provision (benefit)																		141,471		150,322		118,862
NET INCOME		37,365	[1],[2]	$ 65,573		$ 72,336		$ 67,132		46,738	[2],[3]	$ 73,873	[3]	$ 54,336	[3]	$ 69,136	[3]	242,406	[1],[2]	244,083	[2],[3]	233,506
Property, plant and equipment — net		6,109,639								5,496,875								6,109,639		5,496,875		4,846,526
Goodwill		950,163								950,163								950,163		950,163		950,163
Total assets	[4]	7,582,122								6,959,578	[5]							7,582,122		6,959,578	[5]	6,265,018	[5]
Capital expenditures																		684,140		733,145		821,588
Regulated Operating Subsidiaries
Segment Reporting Information
Operating revenues																		1,044,311		1,023,170		941,571
Depreciation and amortization																		143,956		127,320		117,924
Interest expense — net																		97,337		81,225		70,239
Income (loss) before income taxes																		529,484		548,704		515,327
Income tax provision (benefit)																		200,582		210,914		193,764
NET INCOME																		328,902		337,790		321,563
Property, plant and equipment — net		6,093,499								5,483,093								6,093,499		5,483,093		4,833,545
Goodwill		950,163								950,163								950,163		950,163		950,163
Total assets	[4]	7,479,286								6,854,387	[5]							7,479,286		6,854,387	[5]	6,159,153	[5]
Capital expenditures																		687,988		736,751		824,165
ITC Holdings and Other
Segment Reporting Information
Operating revenues																		1,057		605		567
Depreciation and amortization																		716		716		672
Interest expense — net																		106,442		105,418		98,660
Income (loss) before income taxes																		(145,607)		(154,299)		(162,959)
Income tax provision (benefit)																		(59,111)		(60,592)		(74,902)
NET INCOME																		242,406		244,083		233,506
Property, plant and equipment — net		16,140								13,782								16,140		13,782		12,981
Total assets	[4]	4,158,986								3,944,318	[5]							4,158,986		3,944,318	[5]	3,619,759	[5]
Capital expenditures																		3,428		1,471		2,208
Reconciliations and Eliminations
Segment Reporting Information
Operating revenues																		600		727		866
Interest expense — net																				7		580
NET INCOME																		328,902		337,790		321,563
Total assets	[4]	$ 4,056,150								$ 3,839,127	[5]							4,056,150		3,839,127	[5]	3,513,894	[5]
Capital expenditures																		$ 7,276		$ 5,077		$ 4,785

[1] During the third and fourth quarters of 2015, we recognized an aggregate regulatory liability for the refund relating to the formula rate template modifications filing as described in Note 4, which resulted in a reduction in operating revenues and operating income of $9.5 million and an estimated $6.2 million reduction to net income for the year ended December 31, 2015.

[2] During the year ended December 31, 2015 and the fourth quarter of 2014, we recognized an aggregate estimated regulatory liability for the potential refunds relating to the ROE complaints as described in Note 16, which resulted in a reduction in operating revenues and operating income of $115.1 million and $46.9 million and an estimated $73.2 million and $28.9 million reduction to net income for the years ended December 31, 2015 and 2014, respectively.

[3] During the second quarter of 2014, we incurred a loss on extinguishment of debt of $29.2 million related to the tender of ITC Holdings Senior Notes as described in Note 8, which resulted in an estimated reduction to net income of $18.2 million.

[4] Reconciliation of total assets results primarily from differences in the netting of deferred tax assets and liabilities at our Regulated Operating Subsidiaries as compared to the classification in our consolidated statements of financial position.

[5] Amounts reflect the change in the authoritative guidance on the presentation of deferred income taxes on the balance sheet. Refer to Notes 3 and 10 for more information.