Condensed Consolidated Statements of Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Operating Revenues	$ 1,470	$ 1,487	$ 4,651	$ 4,729
Operating Expenses
Purchased power, natural gas and fuel used	259	279	999	1,101
Operations and maintenance	634	588	1,788	1,714
Depreciation and amortization	255	237	748	681
Taxes other than income taxes	157	144	469	446
Total Operating Expenses	1,305	1,248	4,004	3,942
Operating Income	165	239	647	787
Other Income and (Expense)
Other income	16	6	15	1
Earnings (losses) from equity method investments	1	(1)	(3)	1
Interest expense, net of capitalization	(86)	(72)	(251)	(226)
Income Before Income Tax	96	172	408	563
Income tax expense	15	33	21	103
Net Income	81	139	387	460
Net loss attributable to noncontrolling interests	6	11	28	17
Net Income Attributable to Avangrid, Inc.	$ 87	$ 150	$ 415	$ 477
Earnings Per Common Share, Basic (in usd per share)	$ 0.28	$ 0.48	$ 1.34	$ 1.54
Earnings Per Common Share, Diluted (in usd per share)	$ 0.28	$ 0.48	$ 1.34	$ 1.54
Weighted-average Number of Common Shares Outstanding:
Basic (in shares)	309,491,082	309,491,082	309,496,234	309,491,082
Diluted (in shares)	309,550,126	309,517,778	309,554,838	309,512,301