Income Taxes (Income Tax Contingency and Taxes Paid Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Abstract]
Operating Loss Carryforwards, Valuation Allowance		$ 489
Unrecognized benefit that would affect the effective tax rate		7
Amount of interest and penalties included in liabilities for uncertain tax positions		$ 4
Effective Income Tax Rate, Continuing Operations		15.80%	6.10%	28.40%
U.S. federal corporate tax rate		35.00%	35.00%	35.00%
Tax Cuts and Jobs Act of 2017, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)		$ 32
Current provision for income taxes		5	$ 12	$ 14
Cash Paid for Income Taxes, Net of Refunds Received [Abstract]
Cash paid for income taxes (refunds received), net		$ 4	$ (16)	$ 12
Adjusted for the Expense Related to Income Attributable to Noncontrolling Interest [Member]
Income Tax Contingency [Abstract]
Effective Income Tax Rate, Continuing Operations		15.50%	5.70%	37.60%
Scenario, Plan [Member]
Income Tax Contingency [Abstract]
U.S. federal corporate tax rate	21.00%