Parent Company Only Financial Statements Condensed statements of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net income	$ 6,797	$ 5,308	$ 4,929	$ 4,806	$ 26,684	$ 21,840	$ 16,512
Depreciation, amortization and accretion, net					8,134	7,936	4,442
Increase in other assets					668	1,802	169
Increase (decrease) in other liabilities					666	(2,875)	(762)
Net cash provided by operating activities					46,154	27,422	21,998
Cash Acquired from Acquisition					0	36,774	276,661
Net cash provided by (used in) investing activities					(55,962)	(78,059)	10,369
Repayment of short-term debt					(4,000)	(3,938)	(2,000)
Proceeds from short-term debt					0	7,000	2,000
Repayments of Long-term Debt					(3,750)	0	0
Proceeds from long-term debt					0	15,000	0
Proceeds from issuance of common stock					4,399	195	28,222
Direct expenses related to capital transactions					(216)	(229)	0
Purchase of treasury stock					(797)	0	(1,066)
Dividends paid on preferred stock					0	(1,286)	(2,002)
Dividends paid on common stock					(7,228)	(5,277)	(3,487)
Net cash provided by (used in) financing activities					(77,215)	110,755	31,687
Increase (decrease) in cash					(87,023)	60,118	64,054
Cash and cash equivalents at beginning of period				115,784	175,902	115,784	51,730
Cash and cash equivalents at end of period	175,902				88,879	175,902	115,784
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income					26,684	21,840	16,512
Depreciation, amortization and accretion, net					82	87	87
Dividends from subsidiaries					18,925	19,475	6,094
Equity in undistributed earnings of subsidiaries					(9,570)	(4,717)	(11,934)
Increase in other assets					(19,348)	(111,379)	(4,707)
Increase (decrease) in other liabilities					733	153	37
Net cash provided by operating activities					17,506	(74,541)	6,089
Payments to Acquire Additional Interest in Subsidiaries					0	(5,000)	(27,825)
Cash Acquired from Acquisition					0	68,798	0
Net cash provided by (used in) investing activities					0	63,798	(27,825)
Repayment of short-term debt					(4,000)	(3,000)	0
Proceeds from short-term debt					0	7,000	0
Repayments of Long-term Debt					(3,750)	(938)	0
Proceeds from long-term debt					0	15,000	0
Proceeds from issuance of common stock					4,399	195	28,222
Direct expenses related to capital transactions					(216)	(229)	0
Purchase of treasury stock					(797)	0	(1,066)
Dividends paid on preferred stock					0	(1,286)	(2,002)
Dividends paid on common stock					(7,228)	(5,277)	(3,487)
Net cash provided by (used in) financing activities					(11,592)	11,465	21,667
Increase (decrease) in cash					5,914	722	(69)
Cash and cash equivalents at beginning of period				$ 1,660	2,382	1,660	1,729
Cash and cash equivalents at end of period	$ 2,382				$ 8,296	$ 2,382	$ 1,660