Investments (Unconsolidated Equity Investments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	$ (15)	$ (13)
ATC Holdings [Member]
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	(11)	(11)
Other [Member]
Schedule of Equity Method Investments [Line Items]
Equity income from unconsolidated investments, net	$ (4)	$ (2)