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Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share Basic [Abstract]
Net income	$ 23,948	$ 17,890	$ 34,748	$ 37,290
Basic weighted average common shares	19,280,684	19,245,592	19,273,347	19,237,401
Basic earnings per common share	$ 1.24	$ 0.93	$ 1.80	$ 1.94
Net income	$ 23,948	$ 17,890	$ 34,748	$ 37,290
Weighted average common shares	19,280,684	19,245,592	19,273,347	19,237,401
Stock options and restricted stock	55,023	61,361	62,401	78,875
Diluted weighted average common shares	19,335,707	19,306,953	19,335,748	19,316,276
Diluted earnings per common share	$ 1.24	$ 0.93	$ 1.80	$ 1.93

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Incremental common shares attributable to share based payment arrangements stock options and restricted stock.

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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