Equity (Share Repurchases Authorizations) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 05, 2019	Dec. 31, 2017
Under December 2018 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount	$ 1,500
Increased Under September 2019 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount				$ 2,000
Under December 2017 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount			$ 2,500
Under December 2016 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount					$ 1,500
Other common stocks | Increased Under September 2019 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Number of Treasury Stock Shares Acquired	6.7
Other common stocks | Under December 2017 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Number of Treasury Stock Shares Acquired		27.2
Other common stocks | Under December 2016 Board Of Directors Authorization
Equity, Class of Treasury Stock [Line Items]
Number of Treasury Stock Shares Acquired			14.9