Consolidated Statements of Stockholders' Equity - USD ($)
$ in Millions
Total
Preferred Stock
Common Stock
Additional Paid in Capital
Accumulated Other Comprehensive Income (Loss)
Retained Earnings (Accumulated Deficit)
Shares, Outstanding, Beginning Balance at Dec. 31, 2012   266,657 55,863,053      
Beginning Balance at Dec. 31, 2012 $ 1,160 $ 260 $ 1 $ 1,477 $ (2) $ (576)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Net income (loss) 267         267
Total other comprehensive income (loss) (3)       (3)  
Accretion of preferred stock 0 $ 6       (6)
Stock-based compensation (in shares)     275,021      
Stock-based compensation 2     2    
Shares, Outstanding, Ending Balance at Dec. 31, 2013   266,657 56,138,074      
Ending Balance at Dec. 31, 2013 1,426 $ 266 $ 1 1,479 (5) (315)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Net income (loss) (69)         (69)
Total other comprehensive income (loss) 13       13  
Accretion of preferred stock 0 $ 1       (1)
Stock-based compensation (in shares)     194,233      
Stock-based compensation 3     3    
Shares, Outstanding, Ending Balance at Dec. 31, 2014   266,657 56,332,307      
Ending Balance at Dec. 31, 2014 1,373 $ 267 $ 1 1,482 8 (385)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Net income (loss) 78         78
Total other comprehensive income (loss) 0          
Stock-based compensation (in shares)     103,719      
Stock-based compensation 0          
Shares, Outstanding, Ending Balance at Jun. 30, 2015   266,657 56,436,026      
Ending Balance at Jun. 30, 2015 1,451 $ 267 $ 1 1,482 8 (307)
Shares, Outstanding, Beginning Balance at Dec. 31, 2014   266,657 56,332,307      
Beginning Balance at Dec. 31, 2014 1,373 $ 267 $ 1 1,482 8 (385)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Net income (loss) 158         158
Total other comprehensive income (loss) (6)       (6)  
Stock-based compensation (in shares)     150,951      
Stock-based compensation 3     3    
Warrant exercise 1     1   0
Shares, Outstanding, Ending Balance at Dec. 31, 2015   266,657 56,483,258      
Ending Balance at Dec. 31, 2015 1,529 $ 267 $ 1 1,486 2 (227)
Increase (Decrease) in Stockholders' Equity [Roll Forward]            
Net income (loss) 86         86
Total other comprehensive income (loss) (21)       (21)  
Stock-based compensation (in shares)     92,521      
Stock-based compensation 5     5    
Shares, Outstanding, Ending Balance at Jun. 30, 2016   266,657 56,575,779      
Ending Balance at Jun. 30, 2016 $ 1,599 $ 267 $ 1 $ 1,491 $ (19) $ (141)