Parent Company Only Financial Statements Condensed statements of income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	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]
Income before income taxes	$ 13,145	$ 10,965	$ 13,142	$ 11,253	$ 9,122	$ 11,133	$ 12,127	$ 9,344	$ 48,505	$ 41,726	$ 33,780
Income tax benefit	(3,206)	(2,731)	(3,105)	(2,863)	(4,497)	(3,538)	(3,927)	(3,080)	(11,905)	(15,042)	(11,940)
Net income available to common stockholders	$ 9,939	$ 8,234	$ 10,037	$ 8,390	$ 4,625	$ 7,595	$ 8,200	$ 6,264	36,600	26,684	21,015
Other Comprehensive Income (Loss), Net of Tax									(4,169)	3,525	(6,484)
Comprehensive income									32,431	30,209	15,356
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from subsidiaries									21,694	18,925	19,475
Other income									171	1,227	66
Total income									21,865	20,152	19,541
Operating expenses									5,424	3,902	3,491
Income before income taxes									16,441	16,250	16,050
Income tax benefit									1,274	864	1,073
Income before equity in undistributed earnings of subsidiaries									17,715	17,114	17,123
Equity in undistributed earnings of subsidiaries									18,885	9,570	4,717
Net income available to common stockholders									36,600	26,684	21,840
Other Comprehensive Income (Loss), Net of Tax									(4,169)	3,525	(6,484)
Comprehensive income									$ 32,431	$ 30,209	$ 15,356