CONSOLIDATED STATEMENT OF INCOME (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
CONSOLIDATED STATEMENT OF INCOME (Unaudited) [Abstract]
Operating Revenues	$ 293,026	$ 316,478	$ 1,198,982	$ 1,183,591
Operation
Purchased power	37,962	37,314	123,771	105,996
Natural gas purchased	30,814	37,343	322,296	315,520
Operation and maintenance	95,251	89,810	290,828	273,539
Transmission wholesale	25,802	28,659	65,777	65,994
Depreciation and amortization (Note F)	35,578	50,761	112,408	146,537
Taxes - other than income taxes (Note F)	32,897	32,389	102,974	96,335
Rate case disallowances	0	17,543	0	17,543
Acquisition-related expenses (Note A)	570	0	6,090	0
Total Operating Expenses	258,874	293,819	1,024,144	1,021,464
Operating Income	34,152	22,659	174,838	162,127
Other Income and (Deductions), net
Acquisition-related bridge facility fees (Note A)	(849)	0	(15,188)	0
Other income and (deductions) (Note F)	4,336	5,153	12,822	15,718
Total Other Income and (Deductions), net	3,487	5,153	(2,366)	15,718
Interest Charges, net
Interest on long-term debt	22,386	21,896	67,286	65,272
Other interest, net	636	(106)	1,203	2,442
Interest charges, gross	23,022	21,790	68,489	67,714
Amortization of debt expense and redemption premiums	619	609	1,833	1,819
Total Interest Charges, net	23,641	22,399	70,322	69,533
Income from Equity Investments	3,492	3,930	10,398	11,590
Income Before Income Taxes	17,490	9,343	112,548	119,902
Income Taxes (Note E)	4,986	4,186	35,276	45,004
Net Income	12,504	5,157	77,272	74,898
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	6	13	(21)	39
Net Income attributable to UIL Holdings	$ 12,498	$ 5,144	$ 77,293	$ 74,859
Average Number of Common Shares Outstanding - Basic (in shares)	56,855	50,989	56,827	50,956
Average Number of Common Shares Outstanding - Diluted (in shares)	57,133	51,231	57,114	51,237
Earnings Per Share of Common Stock - Basic (Note A) (in dollars per share)	$ 0.22	$ 0.10	$ 1.36	$ 1.47
Earnings Per Share of Common Stock - Diluted (Note A) (in dollars per share)	$ 0.22	$ 0.10	$ 1.35	$ 1.46
Cash Dividends Declared per share of Common Stock (in dollars per share)	$ 0.432	$ 0.432	$ 1.296	$ 1.296