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Stock-Based Compensation (Narrative) (Details) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares reserved for future issuance (in shares) 4,400,000    
Non-employee directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense $ 1    
Stock options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Options outstanding (in shares) 369,050 721,690  
Options, weighted average exercise price (in usd per share) $ 26.74 $ 25.32  
Stock options granted (in shares) 0 0 0
Aggregate intrinsic value of options exercised $ 8 $ 5 $ 12
Aggregate intrinsic value of options outstanding $ 10    
Weighted average remaining contractual life for outstanding stock options exercisable (in years) 5 months    
Unrecognized compensation cost $ 1    
Time-vested restricted stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period (in years) for shares awarded 3 years    
Performance-based shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Level of performance achieved based on shares awarded, minimum 0.00%    
Level of performance achieved based on shares awarded, maximum 200.00%    
Time-vested deferred stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 4 years    
Restricted stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation cost $ 30    
Weighted average recognition period, in years 1 year 9 months    
Aggregate market value of the shares released and issued on the vesting dates $ 26