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Embedded Derivatives - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Jul. 31, 2012
Dec. 31, 2016
Dec. 31, 2015
Derivative [Line Items]      
Estimated fair value of the embedded derivatives   $ 0 $ 0
2022 Notes      
Derivative [Line Items]      
Percentage of convertible senior notes embedded derivatives 7.50%    
7.5% convertible senior notes, maturity date 2022    
2022 notes, conversion date Jul. 01, 2017 Jul. 01, 2017