Subsequent Events Subsequent Events (Common Stock Repurchases) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Feb. 14, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Event [Line Items]
Treasury Stock, Shares, Acquired		49,131,501	88,029,138	56,599,540
Treasury Stock, Value, Acquired, Cost Method		$ 2,285	$ 3,992	$ 2,927
Subsequent Event [Member]
Subsequent Event [Line Items]
Treasury Stock, Shares, Acquired	973,315
Treasury Stock, Value, Acquired, Cost Method	$ 51