Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]		Total
Balance (in shares) at Dec. 31, 2016	22,617
Balance at Dec. 31, 2016	$ 36,250	$ 26,682	$ 252,439	$ (1,499)		$ 313,872
Net income			33,097			33,097
Other comprehensive income, net of tax				968		968
Stock compensation expense		2,012				2,012
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award (in shares)	59
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award	$ 198	2,142	(4,669)			(2,329)
Cash dividends			(13,365)			(13,365)
Shares cancelled (in shares)	(7)
Shares cancelled	$ (24)	(155)	179
Balance (in shares) at Sep. 30, 2017	22,669
Balance at Sep. 30, 2017	$ 36,424	30,681	267,681	(531)		334,255
Balance at Jun. 30, 2017				(610)
Net income						11,704
Other comprehensive income, net of tax				79		79
Balance (in shares) at Sep. 30, 2017	22,669
Balance at Sep. 30, 2017	$ 36,424	30,681	267,681	(531)		334,255
Balance (in shares) at Dec. 31, 2017	22,679
Balance at Dec. 31, 2017	$ 36,457	31,924	267,193	(1,930)	[1]	333,644
Net income			40,859			40,859
Other comprehensive income, net of tax				(6,200)		(6,200)
Stock compensation expense		2,923				2,923
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award (in shares)	71
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award	$ 236	879	(3,224)			(2,109)
Cash dividends			(16,137)			(16,137)
Shares cancelled (in shares)	(4)
Shares cancelled	$ (15)	(128)	143
Reclassification adjustment under Accounting Standard Update 2018-02 at Dec. 31, 2017			506	(506)
Balance (in shares) at Sep. 30, 2018	22,746
Balance at Sep. 30, 2018	$ 36,678	35,598	289,340	(8,636)		352,980
Balance at Jun. 30, 2018				(7,044)
Net income						13,876
Other comprehensive income, net of tax				(1,592)		(1,592)
Balance (in shares) at Sep. 30, 2018	22,746
Balance at Sep. 30, 2018	$ 36,678	$ 35,598	$ 289,340	$ (8,636)		$ 352,980

[1] December 31, 2017 AOCI component balances reflect a correction of incorrectly reported year-end balances in Note 12 of the 2017 Form 10-K, which were presented as $(2,278), $234, and $(392) for securities available-for-sale, cash flow hedges, and minimum pension liability, respectively.