ENTERGY TRANSACTION (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
External Legal, Advisory and Financial Services Fees
Business Acquisition
Transaction related expenses	$ 7.2	$ 5.6	$ 34.9	$ 12.1
Internal Labor and Related Costs
Business Acquisition
Transaction related expenses	1.9	1.9	7.1	5.4
Entergy
Business Acquisition
Transmission lines	15,400		15,400
Ownership percentage of pro forma shares	50.10%		50.10%
Gross cash proceeds for assets	$ 1,775		$ 1,775
ITC Holdings
Business Acquisition
Ownership percentage of pro forma shares	49.90%		49.90%