Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding	559.1	537.4	553.3	536.9
Weighted Average Number of Fully Vested Restricted Stock Units and Performance Share Units Outstanding	1.2	0.4	0.9	0.3
Weighted Average Number of Shares Outstanding, Basic	560.3	537.8	554.2	537.2
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0.5	0.0	0.0	0.0
Weighted Average Number of Shares Outstanding, Diluted	560.8	537.8	554.2	537.2
Net Income (Loss) Available to Common Stockholders, Basic	$ 693	$ (457)	$ (1,749)	$ (202)
Earnings Per Share, Basic	$ 1.24	$ (0.85)	$ (3.16)	$ (0.38)
Earnings Per Share, Diluted	$ 1.24	$ (0.85)	$ (3.16)	$ (0.38)