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Debt - 6.375% Senior Unsecured Notes Due 2022 - Additional Information (Detail) - 6.375% Senior Unsecured Notes Due 2022 [Member] - USD ($)
12 Months Ended
Aug. 20, 2013
Feb. 17, 2012
Dec. 31, 2016
Dec. 31, 2015
Debt Instrument [Line Items]        
Senior unsecured notes face amount $ 150,000,000 $ 200,000,000    
Senior unsecured notes, maturity date   Feb. 15, 2022    
Senior unsecured notes, interest rate   6.375% 6.375% 6.375%
Senior notes, repurchased price percentage on principal amount plus accrued and unpaid interest   101.00%    
Debt instrument redemption price 102.00%      
Debt instrument effective rate 5.998%      
Senior notes frequency of periodic payment     Interest on these notes is payable semi-annually on February 15 and August 15 of each year.  
Senior unsecured notes, redemption description     We may redeem some or all of the notes at a premium that will decrease over time, plus accrued and unpaid interest to, but not including, the redemption date. In the event of a change of control, each holder of the 6.375% Senior Unsecured Notes due 2022 may require us to repurchase some or all of its notes at a repurchase price equal to 101% of the aggregate principal amount plus accrued and unpaid interest to the date of purchase.