Parent Company Financial Statements (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income	$ 18,566	$ 18,322	$ 21,040	$ 11,901	$ 15,536	$ 18,814	$ 17,273	$ 17,495	$ 69,829	$ 69,118	$ 68,432
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in other assets									(57,730)	(27,961)	(7,456)
Change in fair value of contingent consideration liability									0	0	(187)
Tax (expense) benefit from stock option exercises and other equity awards									(103)	248	496
Net cash provided by (used in) operating activities									36,478	73,435	82,876
Cash flows from investing activities:
Net cash provided by (used in) investing activities									(264,240)	(160,115)	(481,831)
Cash flows from financing activities:
Payment of contingent consideration liability									0	0	(1,217)
Treasury stock purchased									(4,322)	0	0
Net proceeds from stock option exercises and issuance of other equity awards, net of awards surrendered									(470)	273	(671)
Cash dividends paid									(35,499)	(34,189)	(29,312)
Net cash provided by (used in) financing activities									291,575	131,660	409,507
Cash and cash equivalents at beginning of year				138,455				93,475	138,455	93,475	82,923
Cash and cash equivalents at end of year	202,268				138,455				202,268	138,455	93,475
Parent Company [Member]
Cash flows from operating activities:
Net income									69,829	69,118	68,432
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in dividend receivable									(2,261)	(1,813)	8
(Increase) decrease in other assets									109	(43)	70
Increase (decrease) in accrued expenses and other liabilities									(31)	(15)	17
Change in fair value of contingent consideration liability									0	0	(187)
Tax (expense) benefit from stock option exercises and other equity awards									(103)	248	496
Other, net									193	(195)	(465)
Net cash provided by (used in) operating activities									40,111	33,842	31,448
Cash flows from financing activities:
Payment of contingent consideration liability									0	0	(1,217)
Treasury stock purchased									(4,322)	0	0
Net proceeds from stock option exercises and issuance of other equity awards, net of awards surrendered									(470)	273	(671)
Cash dividends paid									(35,499)	(34,189)	(29,312)
Net cash provided by (used in) financing activities									(40,291)	(33,916)	(31,200)
Net increase (decrease) in cash and cash equivalents									(180)	(74)	248
Cash and cash equivalents at beginning of year				$ 1,838				$ 1,912	1,838	1,912	1,664
Cash and cash equivalents at end of year	$ 1,658				$ 1,838				1,658	1,838	1,912
Bank [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings (losses) of subsidiaries									(27,603)	(33,445)	(36,876)
Non-bank [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings (losses) of subsidiaries									$ (22)	$ (13)	$ (47)