Parent Company Only Financial Statements Condensed statements of income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Income before income taxes	$ 6,240	$ 6,270	$ 6,460	$ 5,745	$ 5,759	$ 6,262	$ 5,885	$ 5,662	$ 24,715	$ 23,568	$ 22,435
Income tax benefit	(2,330)	(2,355)	(2,431)	(2,138)	(2,140)	(2,352)	(2,220)	(2,134)	(9,254)	(8,846)	(8,410)
Net income	3,910	3,915	4,029	3,607	3,619	3,910	3,665	3,528	15,461	14,722	14,025
Other comprehensive income (loss), net of taxes									7,505	(12,924)	1,396
Comprehensive income									22,966	1,798	15,421
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries									7,900	1,438	1,438
Other income									65	64	64
Total income									7,965	1,502	1,502
Operating expenses									2,425	2,233	2,519
Income before income taxes									5,540	(731)	(1,017)
Income tax benefit									948	876	990
Income (loss) before equity in undistributed earnings of subsidiaries									6,488	145	(27)
Equity in undistributed earnings of subsidiaries									8,973	14,577	14,052
Net income									15,461	14,722	14,025
Other comprehensive income (loss), net of taxes									7,505	(12,924)	1,396
Comprehensive income									$ 22,966	$ 1,798	$ 15,421