Annual report pursuant to Section 13 and 15(d)

Capital Stock - Additional Information (Detail)

v3.8.0.1
Capital Stock - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Stockholders Equity Note [Line Items]      
Preferred stock, shares issued 0    
Preferred stock, shares outstanding 0    
Restricted Stock      
Stockholders Equity Note [Line Items]      
Number of hypothetical shares of common stock 246,534    
Market value of common stock on the dates of grant $ 41.70 $ 30.98 $ 42.79
Unrecognized compensation expense $ 13,049    
Remaining Compensation Expense recognition period (in years) 2 years    
Restricted Stock | Directors      
Stockholders Equity Note [Line Items]      
Award vesting period for restricted stock granted 1 year    
Restricted Stock | Minimum      
Stockholders Equity Note [Line Items]      
Market value of common stock on the dates of grant $ 34.82    
Forfeiture rate for restricted stock awards 0.00%    
Restricted Stock | Minimum | Employees      
Stockholders Equity Note [Line Items]      
Award vesting period for restricted stock granted 1 year    
Restricted Stock | Maximum      
Stockholders Equity Note [Line Items]      
Market value of common stock on the dates of grant $ 42.37    
Forfeiture rate for restricted stock awards 10.00%    
Restricted Stock | Maximum | Employees      
Stockholders Equity Note [Line Items]      
Award vesting period for restricted stock granted 4 years    
Restricted Stock Units (RSUs)      
Stockholders Equity Note [Line Items]      
Number of hypothetical shares of common stock 175,634 253,661 142,917
Market value of common stock on the dates of grant $ 42.37 $ 29.83 $ 43.19
Unrecognized compensation expense $ 6,820    
Remaining Compensation Expense recognition period (in years) 2 years    
Share-based compensation arrangement by share-based payment award, description The financial performance factors are based on an implied equity value concept that determines an internal rate of return (“IRR”) for a two year measurement period, as defined in the award agreement, based on a formula utilizing a multiple of Adjusted EBITDA subject to certain specified adjustments (as defined in the restricted stock unit award agreement).    
Share-based compensation arrangement by share-based payment award, vesting condition All payouts of restricted stock units that vest will be subject to an additional service requirement and will be paid in the form of common stock if the participant continues to provide services through the fourth anniversary of the grant date.    
Internal rate of return, performance period 2 years    
Percentage of IRR expected 11.00%    
Expected forfeiture rate 5.00%    
Number of hypothetical shares of common stock at maximum IRR level 628,189    
Actual cumulative forfeitures (in units) 7,407    
Restricted Stock Units (RSUs) | Stock Grants 2013 and 2014      
Stockholders Equity Note [Line Items]      
Stock price at the date of modification     $ 33.02
Incremental compensation expense     $ 2,460
Restricted Stock Units (RSUs) | Stock Grants 2015      
Stockholders Equity Note [Line Items]      
Stock price at the date of modification   $ 37.98  
Incremental compensation expense   $ 562  
Restricted Stock Units (RSUs) | Stock Grants 2016      
Stockholders Equity Note [Line Items]      
Actual IRR calculated for grant 8.00%    
Restricted Stock Units (RSUs) | Stock Grants 2017      
Stockholders Equity Note [Line Items]      
Actual IRR calculated for grant 9.50%