Stock-Based Compensation (Stock Based Compensation Textuals) (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2016 |
Mar. 31, 2015 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Allocated Share-based Compensation Expense | $ 7 | $ 9 |
| Allocated Share Based Compensation Expense Liability Classified Share-Based Awards | 2 | |
| Restricted Stock [Member] | ||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||
| Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized | $ 45 | |
| Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition | 1 year 11 months 8 days | |
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value | $ 15 | $ 32 |