CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities:
Net income	$ 146,130	$ 118,191
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	11,898	11,946
Amortization of intangible assets	10,300	10,772
Net accretion on securities, loans and borrowings	(17,260)	(7,954)
Stock-based compensation	4,836	4,648
Provision for credit losses	(11,001)	17,313
Amortization of mortgage servicing rights	397	266
Unrealized (gain) loss on equity securities	(14)	30
Income from bank-owned life insurance policies	(1,500)	(1,398)
Net gain on sale of loans and other assets	(408)	(1,633)
Change in other assets and other liabilities	9,646	(26,944)
Net cash provided by operating activities	153,024	125,237
Investing activities:
Proceeds from maturities, calls, and paydowns of available-for-sale investment securities	313,913	219,503
Proceeds from maturities and redemptions of equity and other investment securities	2,652	436
Purchases of available-for-sale investment securities	(1,284,544)	(91,381)
Purchases of equity and other securities	(210)	(3,064)
Net decrease (increase) in loans	141,491	(228,235)
Cash (paid) received for acquisitions, net of cash acquired of $541 and $55,973, respectively	(29,329)	34,360
Purchases of premises and equipment, net	(10,196)	(8,727)
Real estate tax credit investments	(586)	(1,071)
Net cash used in investing activities	(866,809)	(78,179)
Financing activities:
Net increase in deposits	1,498,847	1,609,349
Net decrease in borrowings	29,009	28,690
Payments on subordinated debt held by unconsolidated subsidiary trusts	(77,320)	(2,062)
Issuance of common stock	9,141	14,141
Purchases of treasury stock	(189)	(204)
Sales of treasury stock	0	85
Increase in deferred compensation arrangements	189	204
Cash dividends paid	(67,823)	(64,593)
Withholding taxes paid on share-based compensation	(1,213)	(1,177)
Net cash provided by financing activities	1,390,641	1,584,433
Change in cash and cash equivalents	676,856	1,631,491
Cash and cash equivalents at beginning of period	1,645,805	205,030
Cash and cash equivalents at end of period	2,322,661	1,836,521
Supplemental disclosures of cash flow information:
Cash paid for interest	10,722	16,927
Cash paid for income taxes	34,067	28,705
Supplemental disclosures of noncash financing and investing activities:
Dividends declared and unpaid	23,249	22,658
Transfers from loans to other real estate	281	1,192
Acquisitions:
Common stock issued	0	76,942
Fair value of assets acquired, excluding acquired cash and intangibles	1,324	547,654
Fair value of liabilities assumed	$ 1,101	$ 529,177