CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net income	$ 169,063	$ 168,641	$ 150,717
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	15,891	15,749	16,024
Amortization of intangible assets	15,956	18,155	16,941
Net accretion on securities, loans and borrowings	(6,176)	(9,404)	(6,619)
Stock-based compensation	5,285	6,064	5,137
Provision for loan losses	8,430	10,837	10,984
(Benefit)/provision for deferred income taxes	(2,302)	2,663	(28,692)
Amortization of mortgage servicing rights	378	449	499
Unrealized gain on equity securities	(19)	(657)	0
Loss on debt extinguishment	0	318	0
Income from bank-owned life insurance policies	(1,678)	(1,579)	(1,586)
Gain on sales of investment securities, net	(4,882)	0	(2)
Net loss/(gain) on sale of loans and other assets	11	(80)	181
Change in other assets and liabilities	2,545	10,252	26,090
Net cash provided by operating activities	202,502	221,408	189,674
Investing activities:
Proceeds from sales of available-for-sale investment securities	590,179	0	0
Proceeds from maturities, calls and paydowns of available-for-sale investment securities	209,857	140,784	157,278
Proceeds from maturities and redemptions of other investment securities	3,995	5,867	30,116
Purchases of available-for-sale investment securities	(810,122)	(78,131)	(90,380)
Purchases of equity and other securities	(202)	(31)	(13,302)
Net (increase) decrease in loans	(140,382)	(35,414)	164,846
Cash paid for acquisition, net of cash acquired of $90,381, $16, and $52,132, respectively	(4,653)	(1,737)	(107,414)
Settlement of bank-owned life insurance policies	1,597	0	1,779
Purchases of premises and equipment, net	(5,686)	(12,646)	(10,819)
Real estate limited partnership investments	(1,637)	(1,197)	(733)
Net cash (used in)/provided by investing activities	(157,054)	17,495	131,371
Financing activities:
Net increase (decrease) in deposits	104,435	(122,049)	(79,940)
Net decrease in borrowings, net of payments of $646, $95, and $81,544	(64,405)	(47,339)	(144,809)
Payments on subordinated debt held by unconsolidated subsidiary trusts	(22,681)	(25,207)	0
Issuance of common stock	6,915	6,443	4,563
Purchase of treasury stock	(286)	(298)	(3,306)
Sale of treasury stock	6,884	12,561	10,060
Increase in deferred compensation arrangements	286	298	3,306
Cash dividends paid	(80,241)	(71,495)	(62,305)
Withholding taxes paid on share-based compensation	(3,159)	(1,021)	(1,433)
Net cash used in financing activities	(52,252)	(248,107)	(273,864)
Change in cash and cash equivalents	(6,804)	(9,204)	47,181
Cash and cash equivalents at beginning of year	211,834	221,038	173,857
Cash and cash equivalents at end of year	205,030	211,834	221,038
Supplemental disclosures of cash flow information:
Cash paid for interest	25,425	17,926	13,705
Cash paid for income taxes	46,457	30,266	41,231
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	21,342	19,808	17,460
Transfers from loans to other real estate	2,522	3,299	3,518
Acquisitions:
Common stock issued	0	0	343,132
Fair value of assets acquired, excluding acquired cash and intangibles	548,856	115	1,961,246
Fair value of liabilities assumed	$ 589,733	$ 31	$ 1,870,449