CONSOLIDATED STATEMENT OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENT OF INCOME [Abstract]
Operating Revenues	$ 1,618,716	$ 1,486,501	$ 1,570,094
Operation
Purchased power	139,135	154,546	180,149
Natural gas purchased	438,189	370,234	429,079
Operation and maintenance	384,029	356,277	381,814
Transmission wholesale	88,206	79,469	77,997
Depreciation and amortization (Note F)	189,856	181,348	167,462
Taxes - other than income taxes (Note F)	130,458	114,037	114,211
Regulatory disallowances	8,354	0	0
Total Operating Expenses	1,378,227	1,255,911	1,350,712
Operating Income	240,489	230,590	219,382
Other Income and (Deductions), net (Note F), (Note H)	20,633	25,246	26,932
Interest Charges, net
Interest on long-term debt	87,232	86,469	87,394
Other interest, net (Note F)	2,106	3,636	5,216
Interest Charges, gross	89,338	90,105	92,610
Amortization of debt expense and redemption premiums	2,431	2,437	2,775
Total Interest Charges, net	91,769	92,542	95,385
Income from Equity Investments	15,272	15,273	11,282
Income Before Income Taxes	184,625	178,567	162,211
Income Taxes (Note E)	69,308	74,866	62,501
Net Income (Loss)	115,317	103,701	99,710
Less: Preferred Stock Dividends of Subsidiary, Noncontrolling Interests	52	64	54
Net Income attributable to UIL Holdings	$ 115,265	$ 103,637	$ 99,656
Average Number of Common Shares Outstanding - Basic (in shares)	52,415	50,831	50,609
Average Number of Common Shares Outstanding - Diluted (in shares)	52,711	51,108	50,926
Earnings Per Share of Common Stock - Basic (Note A) (in dollars per share)	$ 2.20	$ 2.04	$ 1.96
Earnings Per Share of Common Stock - Diluted (Note A) (in dollars per share)	$ 2.18	$ 2.02	$ 1.95
Cash Dividends Declared per share of Common Stock (in dollars per share)	$ 1.728	$ 1.728	$ 1.728