Computation of Earnings Per Share - Summary of Calculation of Basic Earnings Per Common Share and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income	$ 17,603	$ 13,275	$ 28,990	$ 23,850
Denominator:
Denominator for basic earnings per share–weighted average common shares	25,501	25,030	25,477	25,014
Effect of dilutive stock options	100	43	108	45
Effect of other common stock equivalents	399	510	397	501
Denominator for diluted earnings per share–adjusted weighted average common shares	26,000	25,583	25,982	25,560
Basic Earnings Per Share	$ 0.69	$ 0.53	$ 1.14	$ 0.95
Diluted Earnings Per Share	$ 0.68	$ 0.52	$ 1.12	$ 0.93