v3.19.2

Divestitures (Details) $ in Millions	3 Months Ended				6 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2019 USD ($)		Jun. 30, 2018 USD ($)		Jul. 10, 2019 MW
Business Acquisition [Line Items]
Dividends paid(2)				$ (20)	$ 0	[1]	$ (18)	[1]
Impairment losses		$ 40	$ 0		$ 55		$ 0
Subsequent Event [Member]
Business Acquisition [Line Items]
Dividends paid(2)	$ 400
Subsequent Event [Member] | Garrison Energy Center and RockGen Energy LLC [Member]
Business Acquisition [Line Items]
Ownership percentage of acquiree									100.00%
Proceeds from Sale of Productive Assets	$ 360
Subsequent Event [Member] | Garrison Energy Center LLC [Member]
Business Acquisition [Line Items]
Power generation capacity | MW									309
Subsequent Event [Member] | RockGen Energy LLC [Member]
Business Acquisition [Line Items]
Power generation capacity | MW									503
[1] Subsequent to the consummation of the Merger on March 8, 2018, we paid certain Merger-related costs incurred by CPN Management, our direct parent.

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