Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Carrying value	$ 508	$ 476	$ 458
Equity (income) / loss	(62)	(61)	(53)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	338	331
Equity (income) / loss	$ (43)	(47)	(45)
ATC LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	16.00%
ATC Holdco LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	20.00%
Non-utility wind farm in Oklahoma [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Carrying value	$ 99	103
Equity (income) / loss	(4)	(8)	(5)
Corporate venture investments [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	52	31
Equity (income) / loss	(13)	(4)	(1)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	19	11
Equity (income) / loss	(2)	(2)	(2)
Total [Member]
Schedule of Equity Method Investments [Line Items]
Carrying value	508	476
Equity (income) / loss	$ (62)	$ (61)	$ (53)