Stock-Based Compensation (Unrecognized Compensation Costs) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 53
Weighted Average to be Recognized	1 year 26 days
Restricted Stock
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 12
Weighted Average to be Recognized	1 year 1 month 2 days
Performance Shares
Share Based Compensation Unrecognized and Non-Vested Cost [Line Items]
Unrecognized Compensation Cost	$ 41
Weighted Average to be Recognized	1 year 22 days