Parent Company Only Financial Statements Condensed statements of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income	$ 4,654	$ 3,663	$ 4,156	$ 4,039	$ 3,910	$ 3,915	$ 4,029	$ 3,607	$ 16,512	$ 15,461	$ 14,722
Depreciation, amortization and accretion, net									4,442	3,960	4,661
Increase in other assets									169	306	3,805
Increase (decrease) in other liabilities									(762)	(724)	401
Repayment of short-term debt									(2,000)	(1,000)	0
Proceeds from short-term debt									2,000	1,000	0
Conversion of preferred stock to shares of common stock									0	24,635	0
Proceeds from issuance of common stock									28,222	25,123	1,303
Purchase of treasury stock									(1,066)	(1,763)	(4,619)
Dividends paid on preferred stock									(2,002)	(4,339)	(4,050)
Dividends paid on common stock									(3,487)	(2,648)	(2,014)
Decrease in cash									64,054	(13,372)	(17,610)
Cash and cash equivalents at beginning of period				51,730				65,102	51,730	65,102
Cash and cash equivalents at end of period	115,784				51,730				115,784	51,730	65,102
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income									16,512	15,461	14,722
Depreciation, amortization and accretion, net									87	110	116
Dividends from subsidiaries									6,094	7,900	1,438
Equity in undistributed earnings of subsidiaries									(11,934)	(8,973)	(14,577)
Increase in other assets									(4,707)	(7,412)	(1,512)
Increase (decrease) in other liabilities									37	260	180
Net cash provided by operating activities									6,089	7,346	367
Payments to Acquire Additional Interest in Subsidiaries									(27,825)	0	0
Net cash provided by (used in) investing activities									(27,825)	0	0
Conversion of preferred stock to shares of common stock									0	24,635	0
Proceeds from issuance of common stock									28,222	25,123	1,303
Purchase of treasury stock									(1,066)	(1,763)	(4,619)
Dividends paid on preferred stock									(2,002)	(4,339)	(4,050)
Dividends paid on common stock									(3,487)	(2,648)	(2,014)
Net cash provided by (used in) financing activities									21,667	(8,262)	(9,380)
Decrease in cash									(69)	(916)	(9,013)
Cash and cash equivalents at beginning of period				$ 1,729				$ 2,645	1,729	2,645	11,658
Cash and cash equivalents at end of period	$ 1,660				$ 1,729				$ 1,660	$ 1,729	$ 2,645