Annual report pursuant to Section 13 and 15(d)

Common Stock and Stockholders' Equity - Summary of Long-Term Incentive Plans (Detail)

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Common Stock and Stockholders' Equity - Summary of Long-Term Incentive Plans (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Allocated Share-based Compensation Expense $ 8.4 $ 9.3 $ 9.4
Shares      
Nonvested beginning balance, shares 3,344,813    
Granted, shares 2,996,151   2,602,973
Vested, shares (1,463,494)    
Forfeited, shares (103,062)    
Nonvested ending balance, shares   3,344,813  
Weighted Average Grant-Date Fair Value      
Nonvested beginning balance (in usd per share) $ 5.66    
Granted (in usd per share) 3.08 $ 6.66 $ 4.77
Vested (in usd per share) 5.48    
Forfeited (in usd per share) 5.74    
Nonvested ending balance (in usd per share) $ 4.08 $ 5.66  
2010 Long-Term Incentive Plan [Member] | Common Stock [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock option outstanding or exercisable (in shares) 1,311,131