SHORT-TERM CREDIT ARRANGEMENTS (Details) (USD $)	9 Months Ended
	Sep. 30, 2014
UIL [Member]
Disclosure of short-term credit arrangements [Abstract]
Maximum debt restriction amount	$ 1,600,000,000
Debt instrument, consolidated debt to consolidated capital ratio	0.77
Number of days of loan term agreement	364 days
Standby Letters of Credit Due in June 2015 [Member]
Disclosure of short-term credit arrangements [Abstract]
Expiration date	Jun. 16, 2015
Standby Letter of Credit Due 2015 [Member]
Disclosure of short-term credit arrangements [Abstract]
Standby letters of credit outstanding	4,400,000
Expiration date	Jan. 31, 2015
Revolving Credit Facility [Member]
Disclosure of short-term credit arrangements [Abstract]
Expiration date	Nov. 30, 2016
Available credit under the Credit Facility	385,600,000
Amounts outstanding under the Credit Facility	10,000,000
Bridge Facility [Member]
Disclosure of short-term credit arrangements [Abstract]
Amounts outstanding under the Credit Facility	0
Maximum borrowing capacity	1,900,000,000
Bridge Facility [Member] | WGP [Member]
Disclosure of short-term credit arrangements [Abstract]
Borrowing limit	$ 950,000,000