Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net, Current	$ 51		$ 55
Income taxes	3	$ 32
Accounting Stadards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Current Income Tax Expense (Benefit)	$ 2