Parent Company Financial Statements (Statements of Cash Flows) (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
Cash flows from operating activities:
Net income	$ 15,536	$ 18,814	$ 17,273	$ 17,495	$ 17,036	$ 17,511	$ 17,674	$ 16,211	$ 69,118	$ 68,432	$ 45,925
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in other assets									(27,961)	(7,456)	(8,794)
Change in fair value of contingent consideration liability									0	(187)	(643)
Tax benefit from stock option exercises and other equity awards									248	496	508
Net cash provided by (used in) operating activities									73,435	82,876	59,385
Cash flows from investing activities:
Net cash provided by (used in) investing activities									(160,115)	(481,831)	(179,706)
Cash flows from financing activities:
Payment of contingent consideration liability									0	(1,217)	0
Net proceeds from stock option exercises and issuance of other equity awards, net of awards surrendered									273	(671)	366
Cash dividends paid									(34,189)	(29,312)	(26,300)
Net cash provided by (used in) financing activities									131,660	409,507	95,447
Net increase (decrease) in cash and cash equivalents									44,980	10,552	(24,874)
Cash and cash equivalents at beginning of year				93,475	93,475			82,923	93,475	82,923	107,797
Cash and cash equivalents at end of year	138,455				93,475	$ 93,475			138,455	93,475	82,923
Parent Company [Member]
Cash flows from operating activities:
Net income									69,118	68,432	45,925
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in dividend receivable									(1,813)	8	(1,252)
(Increase) decrease in other assets									(43)	70	72
Increase (decrease) in accrued expenses and other liabilities									(15)	17	22
Change in fair value of contingent consideration liability									0	(187)	(643)
Tax benefit from stock option exercises and other equity awards									248	496	508
Other, net									(195)	(465)	(673)
Net cash provided by (used in) operating activities									33,842	31,448	25,855
Cash flows from financing activities:
Payment of contingent consideration liability									0	(1,217)	0
Net proceeds from stock option exercises and issuance of other equity awards, net of awards surrendered									273	(671)	366
Cash dividends paid									(34,189)	(29,312)	(26,300)
Net cash provided by (used in) financing activities									(33,916)	(31,200)	(25,934)
Net increase (decrease) in cash and cash equivalents									(74)	248	(79)
Cash and cash equivalents at beginning of year				$ 1,912				$ 1,664	1,912	1,664	1,743
Cash and cash equivalents at end of year	$ 1,838				$ 1,912				1,838	1,912	1,664
Bank [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings (losses) of subsidiaries									(33,445)	(36,876)	(18,193)
Non-bank [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings (losses) of subsidiaries									$ (13)	$ (47)	$ 89