Stock-based Compensation - Summary of SARs Activity (Detail) - SARs [Member] $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Beginning Balance | shares	553,582
Granted, Shares | shares	148,723
Exercised, Shares | shares	(73,739)
Forfeited, Shares | shares	(11,916)
Shares, Ending Balance | shares	616,650
Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 47.81
Granted, Weighted Average Exercise Price | $ / shares	78.73
Exercised, Weighted Average Exercise Price | $ / shares	44.67
Forfeited, Weighted Average Exercise Price | $ / shares	68.95
Weighted Average Exercise Price, Ending balance | $ / shares	$ 55.23
Weighted Average Remaining Contractual Term, Ending balance	7 years 5 months 15 days
Aggregate Intrinsic Value, Ending balance | $	$ 14,640