Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 230	$ 216
Other Comprehensive Income (Loss)
Unrealized loss during the period on derivatives qualifying as cash flow hedges, net of income tax of $(8.5) and $(10.9), respectively	(23)	(29)
Reclassification to net income of loss on cash flow hedges, net of income taxes of $0.3 and $0.7, respectively	2	2
Other Comprehensive Income (Loss)	(21)	(27)
Comprehensive Income	209	189
Net loss attributable to noncontrolling interests	10	1
Comprehensive Income Attributable to Avangrid, Inc.	$ 219	$ 190