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Equity - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Aug. 31, 2015
Stockholders Equity Note [Line Items]          
Common stock authorized to repurchase by Board         $ 100,000,000
Shares repurchased pursuant to authorization 2,451,523        
Available authorization remaining for repurchase $ 65,000,000   $ 65,000,000    
Convertible notes          
Stockholders Equity Note [Line Items]          
Securities excluded in the calculation of diluted earnings per share 21,292,309   21,292,309    
Equity awards          
Stockholders Equity Note [Line Items]          
Securities excluded in the calculation of diluted earnings per share 163,296 57,514 180,897 66,129