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Long-Term Debt - Additional Information (Detail)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 6 Months Ended
Jan. 31, 2015
$ / shares
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Debt Instrument [Line Items]          
Convertible debt, conversion ratio 16.0173        
Convertible debt, conversion price $ 62.43        
Interest expense | $   $ 2,679 $ 2,609 $ 5,340 $ 5,183
Non-cash interest expense | $   $ 876 $ 806 $ 1,734 $ 1,588
Debt discount, remaining amortization period       3 years 8 months 12 days  
Minimum [Member]          
Debt Instrument [Line Items]          
Cash dividends on common stock 0.275        
Maximum [Member]          
Debt Instrument [Line Items]          
Cash dividends on common stock $ 0.300