Earnings Per Share (Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net income	$ 19,881	$ 15,902	$ 21,383	$ 20,750	$ 15,653	$ 13,781	$ 14,133	$ 12,222	$ 77,916	$ 55,789	$ 27,721
Denominator:
Weighted average shares of common stock outstanding									11,771	11,947	11,924
Effect of dilutive common stock equivalents									346	132	164
Weighted average shares of common stock outstanding									12,117	12,079	12,088
Basic earnings per share
Earnings per share - basic	$ 1.71	$ 1.36	$ 1.80	$ 1.75	$ 1.32	$ 1.15	$ 1.17	$ 1.02	$ 6.62	$ 4.67	$ 2.32
Diluted earnings per share
Earnings per share - diluted	$ 1.66	$ 1.32	$ 1.75	$ 1.70	$ 1.30	$ 1.14	$ 1.16	$ 1.01	$ 6.43	$ 4.62	$ 2.29