Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income tax benefit (expense)	$ 1	$ 0	$ (1)	$ 5
Federal net operating loss carryforwards	1,833		1,833
Federal alternative minimum tax credit carryforwards	46		46
Minimum taxable income needed to fully realize the U.S. federal net deferred tax assets	1,963		1,963
Foreign tax credit carryforwards	8		8
Deferred tax assets related to state net operating loss and tax credit carryforwards	242		242
Gross deferred tax assets related to state net operating loss and tax credit carry forwards that will expire in current year	1		1
Net operating loss and tax credit carryforwards in various foreign jurisdictions	1		1
Valuation allowance against deferred tax assets	$ 980		980		$ 1,023
Increase (decrease) in valuation allowance against deferred tax asset			$ 43
Percentage of change in ownership			50.00%
Period of change in ownership			3 years
Long-term tax-exempt rate	2.50%		2.50%
Time period after the change in which amount of the limitation be increased or decreased by built-in gains or losses			5 years
Approximate annual NOL utilization had an ownership change occurred	$ 101		$ 101