Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Retained earnings	Accumulated other comprehensive income (loss), net
Balance at beginning of the year, shares at Dec. 31, 2015		29,975,000
Balance at the beginning of the year at Dec. 31, 2015	$ 469,970	$ 359,451	$ 107,960	$ 2,559
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock awards granted, net of forfeitures, shares		110,000
Restricted stock awards granted, net of forfeitures	$ 0
Exercise of stock options, shares	37,713	38,000
Exercise of stock options	$ 560	$ 560
Stock-based compensation expense	1,840	1,840
Net excess tax benefits from vesting of restricted stock	103	$ 103
Common stock repurchased, shares		(168,000)
Common stock repurchased	(2,894)	$ (2,894)
Net income	38,918		38,918
Other comprehensive income (loss), net of tax	(5,165)			(5,165)
Common stock issued in business combinations	0
Cash dividends declared on common stock	(21,569)		(21,569)
Balance at end of the year, shares at Dec. 31, 2016		29,955,000
Balance at the end of the year at Dec. 31, 2016	481,763	$ 359,060	125,309	(2,606)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ASU Implementation				0
Restricted stock awards forfeited, shares		(10,000)
Restricted stock awards forfeited	$ 0
Exercise of stock options, shares	12,662	13,000
Exercise of stock options	$ 164	$ 164
Stock-based compensation expense	2,103	$ 2,103
Common stock repurchased, shares		(30,000)
Common stock repurchased	(737)	$ (737)
Net income	41,791		41,791
Other comprehensive income (loss), net of tax	1,526			1,526
Common stock issued in business combinations	0
Cash dividends declared on common stock	(18,305)		(18,305)
Balance at end of the year, shares at Dec. 31, 2017		29,928,000
Balance at the end of the year at Dec. 31, 2017	508,305	$ 360,590	149,013	(1,298)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ASU Implementation				(218)
Restricted stock units vested, net of restricted stock awards forfeited, shares		29,000
Restricted stock units vested, net of restricted stock awards forfeited	$ 0
Exercise of stock options, shares	9,842	10,000
Exercise of stock options	$ 133	$ 133
Stock-based compensation expense	2,744	$ 2,744
Common stock repurchased, shares		(53,000)
Common stock repurchased	(1,704)	$ (1,704)
Net income	53,057		53,057
Other comprehensive income (loss), net of tax	(6,064)			(6,064)
Common stock issued in business combinations, shares		6,960,000
Common stock issued in business combinations	230,043	$ 230,043
Cash dividends declared on common stock	(25,791)		(25,791)
Balance at end of the year, shares at Dec. 31, 2018		36,874,000
Balance at the end of the year at Dec. 31, 2018	$ 760,723	$ 591,806	$ 176,372	(7,455)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
ASU Implementation				$ (93)