Shareholders' Equity - Share-based Compensation, Awards, Unrecognized Compensation (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 89
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 42
Awards Compensation Costs Remaining Weighted Average Vesting Term, (Years)	2 years 1 month
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 47
Awards Compensation Costs Remaining Weighted Average Vesting Term, (Years)	2 years