Earnings per Common Share (Schedule of Basic and Diluted Earnings per Common Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income from continuing operations	$ 476	$ 381	$ 399	$ 1,340
Loss from discontinued operations, net of tax	0	0	(1)	(3)
Net income (loss)	$ 476	$ 381	$ 398	$ 1,337
Basic weighted-average common shares outstanding	375,658	390,205	375,478	397,427
Diluted weighted-average common shares outstanding	377,011	392,604	376,659	399,442
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	400	0	1,000	0
Earnings Per Share, Basic [Abstract]
Net income from continuing operations, basic earnings per common share	$ 1.27	$ 0.98	$ 1.06	$ 3.37
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	(0.01)
Net income, basic earnings per common share	1.27	0.97	1.06	3.36
Earnings Per Share, Diluted [Abstract]
Net income from continuing operations, diluted earnings per common share	1.26	0.97	1.06	3.35
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	0	0	(0.01)
Net income, diluted earnings per common share	$ 1.26	$ 0.97	$ 1.06	$ 3.35