Equity (Common Stock - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Equity [Abstract]
Treasury Stock, Shares, Acquired				36,170,428	10,664,608
Treasury Stock, Value, Acquired, Cost Method	$ 1,113	$ 999	$ 500	$ 2,100	$ 500