SEGMENT INFORMATION (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
OPERATING REVENUES:
Operating revenues		$ 298,044	$ 275,058	$ 578,177	$ 547,545
INCOME BEFORE INCOME TAXES:
Income before income taxes		115,905	115,432	219,885	223,024
NET INCOME:
NET INCOME		70,726	72,336	134,963	139,468
TOTAL ASSETS:
Assets		8,066,966		8,066,966		$ 7,555,322
Regulated operations
OPERATING REVENUES:
Operating revenues	[1]	297,954	274,990	577,970	547,440
INCOME BEFORE INCOME TAXES:
Income before income taxes	[1]	166,639	149,640	319,426	298,458
NET INCOME:
NET INCOME	[1]	102,935	92,081	197,120	183,520
TOTAL ASSETS:
Assets		7,954,645		7,954,645		7,463,557
ITC Holdings and other
OPERATING REVENUES:
Operating revenues		288	209	595	386
INCOME BEFORE INCOME TAXES:
Income before income taxes		50,734	34,208	99,541	75,434
NET INCOME:
NET INCOME		70,726	72,336	134,963	139,468
TOTAL ASSETS:
Assets		4,344,359		4,344,359		4,147,915
Intercompany eliminations
OPERATING REVENUES:
Operating revenues		198	141	388	281
NET INCOME:
NET INCOME		102,935	$ 92,081	197,120	$ 183,520
Reconciliations / Intercompany eliminations
TOTAL ASSETS:
Assets	[2]	$ 4,232,038		$ 4,232,038		$ 4,056,150

[1] Amount includes the results of operations from ITC Interconnection for the period June 1, 2016 through June 30, 2016.

[2] Reconciliation of total assets results primarily from differences in the netting of deferred tax assets and liabilities at our subsidiaries in the regulated operations segment as compared to the classification in our condensed consolidated statements of financial position.