Note 8 - Earnings Per Share - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net income attributable to Clearway Energy, Inc.		$ 39	$ 21	$ (5)	$ 116
Common Class A [Member]
Net income attributable to Clearway Energy, Inc.	[1]	$ 12	$ 7	$ (2)	$ 40
Weighted average number of Class C common shares outstanding - basic (in shares)	[1]	35	35	35	35
Earnings (Losses) per Weighted Average Class A and Class C Common Share - Basic (in dollars per share)	[1]	$ 0.36	$ 0.20	$ (0.04)	$ 1.14
Net income attributable to Clearway Energy, Inc.	[1]	$ 12	$ 7	$ (2)	$ 40
Weighted average number of Class C common shares outstanding - diluted (in shares)	[1]	35	35	35	35
Earnings (Losses) per Weighted Average Class A Common Share - Diluted (in dollars per share)	[1]	$ 0.36	$ 0.20	$ (0.04)	$ 1.14
Weighted average number of common shares outstanding — basic and diluted (in shares)	[1]	35	35	35	35
Common Class C [Member]
Net income attributable to Clearway Energy, Inc.	[1]	$ 27	$ 14	$ (3)	$ 76
Weighted average number of Class C common shares outstanding - basic (in shares)	[1]	73	69	73	67
Earnings (Losses) per Weighted Average Class A and Class C Common Share - Basic (in dollars per share)	[1]	$ 0.36	$ 0.20	$ (0.04)	$ 1.14
Net income attributable to Clearway Energy, Inc.	[1]	$ 27	$ 14	$ (3)	$ 85
Weighted average number of Class C common shares outstanding - diluted (in shares)	[1]	75	69	73	77
Earnings (Losses) per Weighted Average Class A Common Share - Diluted (in dollars per share)	[1]	$ 0.36	$ 0.20	$ (0.04)	$ 1.10
Weighted average number of common shares outstanding — basic and diluted (in shares)	[1]	73	69	73	67

[1] Basic and diluted earnings per share might not recalculate due to presenting values in millions rather than whole dollars.