SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012	Dec. 31, 2012
OPERATING REVENUES:
Operating revenues	$ 238,782		$ 214,801	$ 685,903		$ 608,889
INCOME BEFORE INCOME TAXES:
Income before income taxes	93,672		79,521	251,921		216,311
NET INCOME:
NET INCOME	58,984		51,183	156,569		139,620
TOTAL ASSETS:
Assets	6,172,400			6,172,400			5,564,809
Regulated Operating Subsidiaries
OPERATING REVENUES:
Operating revenues	238,857		214,821	686,128		608,950
INCOME BEFORE INCOME TAXES:
Income before income taxes	131,939		111,849	376,398		307,067
NET INCOME:
NET INCOME	82,291		69,537	234,168		190,576
TOTAL ASSETS:
Assets	6,028,346			6,028,346			5,440,401
ITC Holdings and other
OPERATING REVENUES:
Operating revenues	152		151	455		455
INCOME BEFORE INCOME TAXES:
Income before income taxes	(38,267)		(32,328)	(124,477)		(90,756)
NET INCOME:
NET INCOME	58,984		51,183	156,569		139,620
TOTAL ASSETS:
Assets	3,556,794			3,556,794			3,252,047
Intercompany eliminations
OPERATING REVENUES:
Operating revenues	(227)		(171)	(680)		(516)
NET INCOME:
NET INCOME	(82,291)		(69,537)	(234,168)		(190,576)
Reconciliations and Intercompany Eliminations
TOTAL ASSETS:
Assets	$ (3,412,740)	[1]		$ (3,412,740)	[1]		$ (3,127,639)	[1]

[1] 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 condensed consolidated statements of financial position.