Income Taxes - Textuals (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Examination [Line Items]
Amount related to evaluation for need for valuation allowance against deferred tax assets			$ (731,000,000)
Increase / decrease in valuation allowance against deferred tax assets	$ 124,000,000	$ (19,000,000)
Net deferred tax assets	283,000,000	488,000,000
Valuation allowance	175,000,000	51,000,000
Approximate federal net operating loss carryforwards	477,000,000
Approximate federal alternative minimum tax credit carryforwards	32,000,000
Foreign deferred tax assets	223,000,000
Minimum taxable income needed to fully realize the U.S. federal net deferred tax assets	1,663,000,000
State deferred tax assets	$ 169,000,000
Percentage of change in ownership (more than)	50.00%
Period of change in ownership	3 years
Annual U.S. federal NOL utilization	$ 107,000,000
Unrecognized tax benefits, income tax penalties and interest	0	2,000,000
Total amounts of interest and penalties recognized in consolidated statements of operations	0	0	0
Total amount of unrecognized tax benefit that would affect our effective tax rate	$ 12,000,000	$ 14,000,000	$ 17,000,000
Income tax examinations, possible period for resolution	12 months
Lapse of statutes of limitations	$ 2,000,000
Income taxes receivable	$ 12,000,000
Minimum
Income Tax Examination [Line Items]
Period of statutes of limitations	3 years
Maximum
Income Tax Examination [Line Items]
Period of statutes of limitations	5 years
Domestic Tax Authority
Income Tax Examination [Line Items]
Approximate federal alternative minimum tax credit carryforwards	$ 20,000,000