Parent Company Only Financial Statements Condensed statements of cash flows (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net income	$ 4,625	$ 7,595	$ 8,200	$ 6,264	$ 36,600	$ 26,684	$ 21,840
Depreciation, amortization and accretion, net					7,881	8,134	7,936
Increase in other assets					(4,266)	668	1,802
Increase (decrease) in other liabilities					(7,846)	666	(2,875)
Net cash provided by operating activities					42,175	46,154	27,422
Cash Acquired from Acquisition					56,389	0	36,774
Net cash used in investing activities					(10,961)	(55,962)	(78,059)
Repayment of short-term debt					0	(4,000)	(3,938)
Proceeds from short-term debt					0	0	7,000
Repayments of Long-term Debt					(10,313)	(3,750)	0
Proceeds from long-term debt					0	0	15,000
Proceeds from issuance of common stock					36,645	4,399	195
Payments for Repurchase of Common Stock					(138)	(797)	0
Direct expenses related to capital transactions					(2,309)	(216)	(229)
Dividends paid on preferred stock					0	0	(1,286)
Dividends paid on common stock					(8,792)	(7,228)	(5,277)
Net cash provided by (used in) financing activities					21,307	(77,215)	110,755
Increase (decrease) in cash					52,521	(87,023)	60,118
Cash and cash equivalents at beginning of period				175,902	88,879	175,902	115,784
Cash and cash equivalents at end of period	88,879				141,400	88,879	175,902
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Net income					36,600	26,684	21,840
Depreciation, amortization and accretion, net					90	82	87
Dividends from subsidiaries					21,694	18,925	19,475
Equity in undistributed earnings of subsidiaries					(18,885)	(9,570)	(4,717)
Increase in other assets					(1,645)	(19,348)	(111,379)
Increase (decrease) in other liabilities					79	733	153
Net cash provided by operating activities					37,933	17,506	(74,541)
Payments to Acquire Additional Interest in Subsidiaries					(13,430)	0	(5,000)
Cash Acquired from Acquisition					(29,321)	0	68,798
Net cash used in investing activities					(42,751)	0	63,798
Repayment of short-term debt					0	(4,000)	(3,000)
Proceeds from short-term debt					0	0	7,000
Repayments of Long-term Debt					(10,313)	(3,750)	(938)
Proceeds from long-term debt					0	0	15,000
Proceeds from issuance of common stock					36,645	4,399	195
Payments for Repurchase of Common Stock					(138)	(797)	0
Direct expenses related to capital transactions					(2,309)	(216)	(229)
Dividends paid on preferred stock					0	0	(1,286)
Dividends paid on common stock					(8,792)	(7,228)	(5,277)
Net cash provided by (used in) financing activities					15,093	(11,592)	11,465
Increase (decrease) in cash					10,275	5,914	722
Cash and cash equivalents at beginning of period				$ 2,382	8,296	2,382	1,660
Cash and cash equivalents at end of period	$ 8,296				$ 18,571	$ 8,296	$ 2,382