Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net of Tax [Member]	Total
Balance at Dec. 31, 2015	$ 87,685	$ 217,032	$ 169,855	$ 1,011	$ 475,583
Balance (in shares) at Dec. 31, 2015	17,536,914
Increase (Decrease) in Stockholders' Equity [Roll forward]
Net income			47,346		47,346
Other comprehensive loss, net of tax				(3,315)	(3,315)
Cash dividends declared			(22,123)		(22,123)
Issuance of common stock	$ 693	2,292			2,985
Issuance of common stock (in shares)	138,605
Repurchase of common stock	$ (57)	(325)			(382)
Repurchase of common stock (in shares)	(11,574)
Vesting of restricted stock	$ (265)	265			0
Vesting of restricted stock (in shares)	(52,963)
Issuance of restricted stock	$ 90	(90)			0
Issuance of restricted stock (in shares)	18,069
Forfeiture of restricted stock	$ (2)	2			0
Forfeiture of restricted stock (in shares)	(356)
Stock-based compensation and related excess tax benefits		521			521
Balance at Dec. 31, 2016	$ 88,144	219,697	195,078	(2,304)	500,615
Balance (in shares) at Dec. 31, 2016	17,628,695
Increase (Decrease) in Stockholders' Equity [Roll forward]
Implementation of ASU | Accounting Standards Update 2018-02 [Member]			621	(621)	0
Net income			51,493		51,493
Other comprehensive loss, net of tax				(581)	(581)
Cash dividends declared			(22,924)		(22,924)
Issuance of common stock	$ 276	1,237			1,513
Issuance of common stock (in shares)	55,191
Repurchase of common stock	$ 0	0			0
Repurchase of common stock (in shares)	0
Vesting of restricted stock	$ (60)	60			0
Vesting of restricted stock (in shares)	(11,965)
Issuance of restricted stock	$ 118	(118)			0
Issuance of restricted stock (in shares)	23,668
Forfeiture of restricted stock	$ (13)	13			0
Forfeiture of restricted stock (in shares)	(2,677)
Stock-based compensation and related excess tax benefits		583			583
Balance at Dec. 31, 2017	$ 88,465	221,472	224,268	(3,506)	$ 530,699
Balance (in shares) at Dec. 31, 2017	17,692,912				17,692,912
Increase (Decrease) in Stockholders' Equity [Roll forward]
Implementation of ASU | Accounting Standards Update 2014-09 [Member]			358		$ 358
Implementation of ASU | Accounting Standards Update 2016-01 [Member]			(507)	507	0
Net income			59,228		59,228
Other comprehensive loss, net of tax				(3,612)	(3,612)
Cash dividends declared			(24,412)		(24,412)
Issuance of common stock	$ 211	1,019			1,230
Issuance of common stock (in shares)	42,133
Vesting of restricted stock	$ (60)	60			0
Vesting of restricted stock (in shares)	(11,997)
Issuance of restricted stock	$ 57	(57)			0
Issuance of restricted stock (in shares)	11,320
Forfeiture of restricted stock	$ (8)	8			0
Forfeiture of restricted stock (in shares)	(1,515)
Stock-based compensation		659			659
Balance at Dec. 31, 2018	$ 88,665	$ 223,161	$ 258,935	$ (6,611)	$ 564,150
Balance (in shares) at Dec. 31, 2018	17,732,853				17,732,853