Parent Company Only Financial Information (Statement of Cash Flow) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net income	$ 14,860	$ 14,868	$ 9,598	$ 14,369	$ 13,897	$ 12,725	$ 7,892	$ 11,741	$ 53,695	$ 46,255	$ 38,471
Depreciation, amortization and accretion, net									17,861	18,204	18,142
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on investment securities	(94)	$ (97)	$ 57	(30)	0	$ 0	$ 147	(1)	(164)	146	(2,983)
Net cash provided by operating activities									67,157	75,243	61,027
Investing activities:
Business acquisitions, net of cash received									7,814	4,695	(1,069)
Financing activities:
Payments on long-term borrowings									(3,501)	(4,591)	(5,738)
Proceeds from issuance of common shares									6	25	9
Cash dividends paid									(25,942)	(20,915)	(14,706)
Net cash (used in) provided by financing activities									(30,629)	60,331	107,709
Net increase in cash, cash equivalents and restricted cash									37,581	5,418	6,048
Cash, cash equivalents and restricted cash at beginning of period				77,612				72,194	77,612	72,194	66,146
Cash, cash equivalents, and restricted cash at end of period	115,193				77,612				115,193	77,612	72,194
Supplemental cash flow information:
Payments for Repurchase of Common Stock									805	0	0
Holding Company
Operating activities:
Net income									53,695	46,255	38,471
Depreciation, amortization and accretion, net									168	9,177	(6,525)
Adjustments to reconcile net income to net cash provided by operating activities:
(Equity in) excess dividends from undistributed earnings of subsidiaries									(22,517)	(34,115)	7,590
Gain on investment securities									0	0	(2,602)
Other, net									3,801	31	2,810
Net cash provided by operating activities									35,147	21,348	39,744
Investing activities:
Proceeds from Sale, Maturity and Collection of Investments									0	5,388	2,359
Investment in subsidiaries									(18,874)	(31,813)	(50,883)
Decrease in receivable from subsidiary									18,869	32,236	25,496
Business acquisitions, net of cash received									(1,438)	(637)	0
Payments for (Proceeds from) Other Investing Activities									226	228	(229)
Net cash provided by (used in) investing activities									(1,217)	5,402	(23,257)
Financing activities:
Purchase of treasury stock										(1,380)	(508)
Proceeds from issuance of common shares									6	25	9
Cash dividends paid									(25,942)	(20,915)	(14,706)
Net cash (used in) provided by financing activities									(27,586)	(22,270)	(15,205)
Net increase in cash, cash equivalents and restricted cash									6,344	4,480	1,282
Cash and cash equivalents at the beginning of year					13,800					13,800	9,320	$ 8,038
Cash, cash equivalents and restricted cash at beginning of period				$ 13,800				$ 9,320	13,800	9,320
Cash, cash equivalents, and restricted cash at end of period	$ 20,144				$ 13,800				20,144	13,800	9,320
Supplemental cash flow information:
Interest paid									544	$ 513	$ 364
Payments for Repurchase of Common Stock									$ (1,650)