Condensed Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Operating Revenues	$ 1,331	$ 1,439	$ 3,089	$ 3,109
Operating Expenses
Purchased power, natural gas and fuel used	242	221	707	649
Operations and maintenance	522	558	1,073	1,109
Depreciation and amortization	206	213	403	418
Taxes other than income taxes	138	125	285	262
Total Operating Expenses	1,108	1,117	2,468	2,438
Operating Income	223	322	621	671
Other Income and (Expense)
Other income	8	20	21	69
Earnings from equity method investments	1		3	2
Interest expense, net of capitalization	(68)	(68)	(139)	(152)
Income Before Income Tax	164	274	506	590
Income tax expense	44	172	147	276
Net Income	120	102	359	314
Net Income Attributable to Avangrid, Inc.	$ 120	$ 102	$ 359	$ 314
Earnings Per Common Share, Basic	$ 0.39	$ 0.33	$ 1.16	$ 1.01
Earnings Per Common Share, Diluted	$ 0.39	$ 0.33	$ 1.16	$ 1.01
Weighted-average Number of Common Shares Outstanding:
Basic	309,520,718	309,527,868	309,514,836	309,533,042
Diluted	309,826,185	309,683,965	309,799,839	309,689,138
Cash Dividends Declared Per Common Share	$ 0.432	$ 0.432	$ 0.864	$ 0.864