Investments in Unconsolidated Affiliates (Investments in Equity Method Unconsolidated Affiliates) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments In Unconsolidated Affiliates [Line Items]
Investments	$ 961	$ 1,936	$ 1,409
Equity in (losses) earnings of unconsolidated affiliates	(2,005)	162	83
Electric Utilities and Infrastructure
Investments In Unconsolidated Affiliates [Line Items]
Investments	105	122	97
Equity in (losses) earnings of unconsolidated affiliates	(1)	9	6
Gas Utilities and Infrastructure
Investments In Unconsolidated Affiliates [Line Items]
Investments	215	1,388	1,003
Equity in (losses) earnings of unconsolidated affiliates	(2,017)	114	27
Commercial Renewables
Investments In Unconsolidated Affiliates [Line Items]
Investments	534	314	201
Equity in (losses) earnings of unconsolidated affiliates		(4)	(1)
Other
Investments In Unconsolidated Affiliates [Line Items]
Investments	107	112	108
Equity in (losses) earnings of unconsolidated affiliates	$ 13	$ 43	$ 51