Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	$ 107	$ 107
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount		2
Deferred Tax Assets, Net, Current	$ 51	51		$ 55
Income taxes		3	$ 32
Accounting Stadards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Current Income Tax Expense (Benefit)		$ 2