PARENT COMPANY STATEMENTS - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 18, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities:
Net income		$ 189,694	$ 164,676	$ 169,063
Adjustments to reconcile net income to net cash provided by operating activities
Net change in other assets and other liabilities		2,064	(16,939)	2,545
Net cash provided by operating activities		202,546	179,483	202,502
Investing activities:
Cash paid for acquisitions, net of cash acquired of $0, $448, and $1,328, respectively	$ (500)	(29,329)	34,360	(4,653)
Net cash used in investing activities		(1,530,775)	(398,720)	(157,054)
Financing activities:
Issuance of common stock		9,821	15,792	6,915
Purchase of treasury stock		(5,106)	(271)	(286)
Sale of treasury stock		0	85	6,884
Increase in deferred compensation arrangements		252	271	286
Net cash provided by (used in) financing activities		1,557,488	1,660,012	(52,252)
Change in cash and cash equivalents		229,259	1,440,775	(6,804)
Cash and cash equivalents at beginning of year		1,645,805	205,030	211,834
Cash and cash equivalents at end of year		1,875,064	1,645,805	205,030
Supplemental disclosures of cash flow information:
Cash paid for interest		13,752	21,169	25,425
Supplemental disclosures of noncash financing activities
Dividends declared and unpaid		23,235	22,695	21,342
Common stock issued for acquisition		0	76,942	0
Parent Company
Operating activities:
Net income		189,694	164,676	169,063
Adjustments to reconcile net income to net cash provided by operating activities
Equity in undistributed net income of subsidiaries		(52,648)	(49,789)	(27,753)
Net change in other assets and other liabilities		(3,050)	1,740	86
Net cash provided by operating activities		133,996	116,627	141,396
Investing activities:
Purchases of investment securities		(5,173)	(3,000)	0
Cash paid for acquisitions, net of cash acquired of $0, $448, and $1,328, respectively		0	(20,892)	(92,056)
(Capital contributions to)/Return of capital from		(12,918)	2	100,680
Net cash used in investing activities		(18,091)	(23,890)	8,624
Financing activities:
Repayment of advances from subsidiaries		(482)	(482)	(1,652)
Repayment of borrowings		(77,320)	(12,062)	(22,681)
Issuance of common stock		16,155	22,211	12,200
Purchase of treasury stock		(5,106)	(271)	(286)
Sale of treasury stock		0	85	6,884
Increase in deferred compensation arrangements		252	271	286
Cash dividends paid		(91,051)	(87,131)	(80,241)
Net cash provided by (used in) financing activities		(157,552)	(77,379)	(85,490)
Change in cash and cash equivalents		(41,647)	15,358	64,530
Cash and cash equivalents at beginning of year		196,021	180,663	116,133
Cash and cash equivalents at end of year		154,374	196,021	180,663
Supplemental disclosures of cash flow information:
Cash paid for interest		560	2,555	4,306
Supplemental disclosures of noncash financing activities
Dividends declared and unpaid		23,235	22,695	21,342
Advances from subsidiaries		482	932	1,691
Common stock issued for acquisition		$ 0	$ 76,942	$ 0