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%