Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 81	$ 139	$ 387	$ 460
Other Comprehensive Income (Loss)
Loss on nonqualified pension plans	0	0	0	(1)
Unrealized (loss) gain during the period on derivatives qualifying as cash flow hedges, net of income tax of $(3) and $2 for the three months ended, respectively, and $(8) for both the nine months ended	(15)	5	(31)	(22)
Reclassification to net income of loss on cash flow hedges, net of income taxes of $0 and $1 for both the three months ended, respectively, and $1 and $2 for the nine months ended, respectively	9	5	12	8
Other Comprehensive Income (Loss)	(6)	10	(19)	(15)
Comprehensive Income	75	149	368	445
Net loss attributable to noncontrolling interests	6	11	28	17
Comprehensive Income Attributable to Avangrid, Inc.	81	160	396	462
Unrealized gain (loss) during the period on derivatives qualifying as cash flow hedges, tax	$ (3)	$ 2	$ (8)	$ (8)