Stockholders' Equity, Performance Shares (Details) (Long-Term Incentive Plan [Member], Management [Member], Performance Shares [Member], USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Year of 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,112,330
Fair Value of Share Based Award	$ 22	$ 31
Share Based Award Liability, Current	20
Year of 2012 [Member] | Payable 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	278,084
Fair Value of Share Based Award	5	8
Share Based Award Liability, Current	5
Year of 2012 [Member] | Payable 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	834,246
Fair Value of Share Based Award	17	23
Share Based Award Liability, Current	15
Year of 2013 [Member] | Payable 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,636,572
Fair Value of Share Based Award	39	35
Share Based Award Liability, Current	$ 26