Quarterly report pursuant to Section 13 or 15(d)

Treasury Stock and Share Based Awards - Additional Information (Detail)

v3.8.0.1
Treasury Stock and Share Based Awards - Additional Information (Detail)
$ / shares in Units, $ in Thousands
9 Months Ended
Sep. 30, 2017
USD ($)
$ / shares
shares
Restricted Stock  
Stockholders Equity Note [Line Items]  
Number of hypothetical shares of common stock | shares 237,933
Market value of common stock on the dates of grant | $ / shares $ 41.94
Restricted Stock | Directors  
Stockholders Equity Note [Line Items]  
Award vesting period for restricted stock granted 1 year
Restricted Stock | Employees  
Stockholders Equity Note [Line Items]  
Award vesting period for restricted stock granted 4 years
Unvested Restricted Stock Awards  
Stockholders Equity Note [Line Items]  
Unrecognized compensation expense | $ $ 15,335
Remaining Compensation Expense recognition period (in years) 2 years
Restricted Stock Units (RSUs)  
Stockholders Equity Note [Line Items]  
Number of hypothetical shares of common stock | shares 175,634
Market value of common stock on the dates of grant | $ / shares $ 42.37
Unrecognized compensation expense | $ $ 8,314
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”) during the two fiscal year periods ending December 31, 2018 based on a formula utilizing a multiple of Adjusted EBITDA subject to certain specified adjustments as specified by the Compensation Committee prior to the grant date
Internal rate of return, performance period 2 years
Percentage of IRR, which is the threshold 7.00%
Percentage of IRR, which is the target 9.50%
Percentage of IRR, which is the maximum 13.00%
Percentage of restricted stock units vest 100.00%
Percentage of IRR expected 11.00%
Share-based compensation arrangement by share-based payment award, vesting condition All restricted stock units granted during 2017 will vest subject to an additional two-year service requirement and will be paid in the form of common stock if the participant continues to provide services through February 2021, which is the fourth anniversary of the grant date
Expected forfeiture rate 5.00%
Number of hypothetical shares of common stock at maximum IRR level | shares 628,189
Actual cumulative forfeitures (in units) | shares 7,407
Minimum | Restricted Stock  
Stockholders Equity Note [Line Items]  
Market value of common stock on the dates of grant | $ / shares $ 38.65
Forfeiture rate for restricted stock awards 0.00%
Maximum | Restricted Stock  
Stockholders Equity Note [Line Items]  
Market value of common stock on the dates of grant | $ / shares $ 42.37
Forfeiture rate for restricted stock awards 10.00%
Maximum | Restricted Stock Units (RSUs) | IRR at least 7%  
Stockholders Equity Note [Line Items]  
Vesting percentage of restricted stock units 0.33%
Maximum | Restricted Stock Units (RSUs) | IRR at least 9.5%  
Stockholders Equity Note [Line Items]  
Vesting percentage of restricted stock units 0.67%