Earnings Per Share (Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income	$ 21,935	$ 18,477	$ 21,383	$ 20,750	$ 40,412	$ 42,133
Denominator:
Weighted average shares of common stock outstanding	11,777		11,861		11,774	11,870
Effect of dilutive common stock equivalents	44		357		48	359
Weighted average shares of common stock outstanding	11,821		12,218		11,822	12,229
Basic earnings per share
Earnings per share - basic	$ 1.86		$ 1.80		$ 3.43	$ 3.55
Diluted earnings per share
Earnings per share - diluted	$ 1.86		$ 1.75		$ 3.42	$ 3.45