Shareholders' Equity Narrative (Details) - USD ($) $ / shares in Units, $ in Billions	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock, No Par Value	$ 0
Common Stock, Shares Authorized	1,000,000,000
Preferred Stock, Shares Authorized	500,000
Common Stock, No Par Value	$ 0
Preferred Stock, Shares Issued	0
Treasury Stock, Shares	160,000,000.0	158,800,000
Common Stock [Member]
Treasury Stock, Value	$ 5.2	$ 5.3
Reinvested Earnings [Member]
Treasury Stock, Value	$ 0.3	$ 0.1