Earnings Per Share - Summary of Numerator and Denominator of Basic and Fully Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income	$ 8,936	$ 7,553	$ 9,483	$ 14,291
Less: Income attributable to participating securities	(465)	(405)	(472)	(821)
Basic Earnings Per Share:
Income allocated to common stockholders, Income (Numerator)	$ 8,471	$ 7,148	$ 9,011	$ 13,470
Income allocated to common stockholders, Shares (Denominator)	7,324	7,666	7,347	7,701
Income allocated to common stockholders, Per Share Amount	$ 1.16	$ 0.93	$ 1.23	$ 1.75
Diluted Earnings Per Share:
Income available to common stockholders and assumed conversions, Income (Numerator)	$ 10,419	$ 9,019	$ 9,011	$ 18,338
Income available to common stockholders and assumed conversions, Shares (Denominator)	9,685	10,027	7,353	10,664
Income available to common stockholders and assumed conversions, Per Share Amount	$ 1.08	$ 0.90	$ 1.23	$ 1.72
Convertible Senior Notes [Member]
Effect of Dilutive Securities:
Dilutive Securities, Income (Loss) (Numerator)	$ 1,948	$ 1,871		$ 4,868
Dilutive Securities, Shares (Denominator)	2,357	2,346		2,947
Stock Options [Member]
Effect of Dilutive Securities:
Dilutive Securities, Shares (Denominator)	4	15	6	16