Annual report pursuant to Section 13 and 15(d)

Long-Term Debt - Summary of Company's Current Debt Portfolio (Detail)

v3.8.0.1
Long-Term Debt - Summary of Company's Current Debt Portfolio (Detail) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Jan. 22, 2014
Jul. 30, 2013
Debt Instrument [Line Items]        
Total principal $ 585,000 $ 585,000    
Less: unamortized debt issuance costs (7,029) (8,674)    
Total long-term debt 577,971 576,326    
6.75% Notes, due July 2022        
Debt Instrument [Line Items]        
Total principal 360,000 360,000    
Less: unamortized debt issuance costs $ (4,600)      
Debt instrument fixed interest rate 6.75%   6.75%  
7.50% Senior Notes, due August 2020        
Debt Instrument [Line Items]        
Total principal $ 225,000 $ 225,000    
Less: unamortized debt issuance costs $ (2,400)      
Debt instrument fixed interest rate 7.50%     7.50%