Parent Company Statements (Details 1) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Income Statements, Captions [Line Items]
Interest expense	$ (2,231)	$ (2,183)	$ (2,084)	$ (1,942)	$ (1,809)	$ (1,733)	$ (1,672)	$ (1,567)	$ (8,440)	$ (6,781)	$ (6,559)
Noninterest expense	(18,180)	(18,292)	(17,347)	(17,274)	(17,348)	(16,848)	(16,796)	(16,897)	(71,093)	(67,889)	(66,758)
Income before income taxes and equity in earnings of subsidiaries	10,801	10,039	10,571	10,186	9,307	9,694	9,378	9,454	41,597	37,833	33,455
Net income	$ 7,365	$ 7,045	$ 7,264	$ 7,169	$ 6,563	$ 6,696	$ 6,563	$ 6,601	28,843	26,423	24,292
Comprehensive income									25,436	25,931	27,861
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Dividends from subsidiaries									24,200	30,900	22,200
Interest on investments									0	1	0
Interest expense									(753)	(613)	(587)
Other income									0	1	2
Noninterest expense									(644)	(588)	(861)
Income before income taxes and equity in earnings of subsidiaries									22,803	29,701	20,754
Income tax credit									(466)	(397)	(485)
Income before equity in earnings of subsidiaries									23,269	30,098	21,239
(Distributions in excess of) undistributed equity in earnings of subsidiaries									5,574	(3,675)	3,053
Net income									28,843	26,423	24,292
Comprehensive income									$ 25,436	$ 25,931	$ 27,861