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, 2015	14,919
Balance at Dec. 31, 2015	$ 10,616	$ 44,180	$ 231,091	$ 632	$ 286,519
Net income			30,411		30,411
Other comprehensive income, net of tax				3,809	3,809
Stock compensation expense		1,646			1,646
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award (in shares)	159
Stock issued for share-based awards, net of withholdings to satisfy employee tax obligations upon award	$ 527	3,404	(2,903)		1,028
3 for 2 stock split (in shares)	7,494
3 for 2 stock split	$ 24,956	(24,956)
Cash dividends			(11,843)		(11,843)
Shares cancelled (in shares)	(9)
Shares cancelled	$ (31)	(224)	255
Balance (in shares) at Sep. 30, 2016	22,563
Balance at Sep. 30, 2016	$ 36,068	24,050	247,011	4,441	311,570
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