Recent Accounting Literature (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Payments Related to Tax Withholding for Share-based Compensation	$ 5	$ 10
Accounting Stadards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Current Income Tax Expense (Benefit)	2
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets	$ 1
Payments Related to Tax Withholding for Share-based Compensation		$ 10