Earnings Per Share (Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net income	$ 21,383	$ 20,750	$ 14,133	$ 12,222	$ 42,133	$ 26,355
Denominator:
Weighted average shares of common stock outstanding	11,861		12,037		11,870	12,032
Effect of dilutive common stock equivalents	357		137		359	97
Weighted average shares of common stock outstanding	12,218		12,174		12,229	12,129
Basic earnings per share
Earnings per share	$ 1.80		$ 1.17		$ 3.55	$ 2.19
Diluted earnings per share
Earnings per share	$ 1.75		$ 1.16		$ 3.45	$ 2.17