Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Operating Revenues	$ 1,758	$ 1,670
Operating Expenses
Purchased power, natural gas and fuel used	465	428
Operations and maintenance	551	551
Depreciation and amortization	197	205
Taxes other than income taxes	147	137
Total Operating Expenses	1,360	1,321
Operating Income	398	349
Other Income and (Expense)
Other income	13	49
Earnings from equity method investments	2	2
Interest expense, net of capitalization	(71)	(84)
Income Before Income Tax	342	316
Income tax expense	103	104
Net Income	239	212
Net Income Attributable to Avangrid, Inc.	$ 239	$ 212
Earnings Per Common Share, Basic	$ 0.77	$ 0.69
Earnings Per Common Share, Diluted	$ 0.77	$ 0.69
Weighted-average Number of Common Shares Outstanding:
Basic	309,508,889	309,538,215
Diluted	309,837,442	309,808,006
Cash Dividends Declared Per Common Share	$ 0.432	$ 0.432