Registration of securities issued in business combination transactions

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 $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Nonvested beginning balance, shares 2,813,409    
Granted, shares 1,558,347    
Vested, shares (1,472,233)    
Forfeited, shares (505,626)    
Nonvested ending balance, shares 2,393,897 2,813,409  
Nonvested beginning balance $ 6.91    
Granted $ 5.37 $ 5.61 $ 4.54
Vested $ 4.86    
Forfeited $ 5.44    
Nonvested ending balance $ 5.22 $ 6.91