Stock-Based Compensation (Unrecognized Compensation Costs) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 81
Weighted Average to be Recognized	1 year 2 months 1 day
Stock awards
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 19
Weighted Average to be Recognized	1 year 6 months 25 days
Performance shares
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 62
Weighted Average to be Recognized	1 year 18 days