CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	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:
Depreciation	15,592	15,963	15,891
Amortization of intangible assets	14,051	14,297	15,956
Net accretion on securities, loans and borrowings	(22,501)	(11,353)	(6,176)
Stock-based compensation	6,334	6,419	5,285
Provision for credit losses	(8,839)	14,212	8,430
Provision (benefit) for deferred income taxes	7,989	(2,336)	(2,302)
Amortization of mortgage servicing rights	519	379	378
Unrealized (gain) loss on equity securities	(17)	6	(19)
Gain on debt extinguishment	0	(421)	0
Income from bank-owned life insurance policies	(2,012)	(1,915)	(1,678)
Gain on sales of investment securities, net	0	0	(4,882)
Net (gain) loss on sale of loans and other assets	(328)	(3,505)	11
Change in other assets and liabilities	2,064	(16,939)	2,545
Net cash provided by operating activities	202,546	179,483	202,502
Investing activities:
Proceeds from sales of available-for-sale investment securities	0	0	590,179
Proceeds from maturities, calls and paydowns of available-for-sale investment securities	423,738	885,549	209,857
Proceeds from maturities and redemptions of equity and other securities	2,946	516	3,995
Purchases of available-for-sale investment securities	(1,963,884)	(1,114,914)	(810,122)
Purchases of equity and other securities	(353)	(3,234)	(202)
Net decrease (increase) in loans	49,929	(185,131)	(140,382)
Cash (paid) received for acquisition, net of cash acquired of $541, $55,973, and $90,381, respectively	(29,329)	34,360	(4,653)
Settlement of bank owned life insurance policies	0	0	1,597
Purchases of premises and equipment, net	(13,176)	(14,395)	(5,686)
Real estate limited partnership investments	(646)	(1,471)	(1,637)
Net cash used in investing activities	(1,530,775)	(398,720)	(157,054)
Financing activities:
Net increase in deposits	1,686,194	1,713,733	104,435
Net increase/(decrease) in borrowings, net of payments of $4,769, $3,092, and $646, respectively	35,942	30,908	(64,405)
Payments on subordinated debt held by unconsolidated subsidiary trusts	(77,320)	(2,062)	(22,681)
Payments on subordinated notes payable	0	(10,000)	0
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 agreements	252	271	286
Cash dividends paid	(91,051)	(87,131)	(80,241)
Withholding taxes paid on share-based compensation	(1,244)	(1,313)	(3,159)
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
Cash paid for income taxes	41,531	39,578	46,457
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	23,235	22,695	21,342
Transfers from loans to other real estate	520	1,291	2,522
Acquisitions:
Common stock issued	0	76,942	0
Fair value of assets acquired, excluding acquired cash and intangibles	1,339	547,654	548,856
Fair value of liabilities assumed	$ 1,101	$ 529,177	$ 589,396