Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities
Interest and dividends received	$ 400,867	$ 438,795	$ 363,217
Service charges and other fees received	39,525	42,489	35,915
Interest paid	(13,627)	(21,193)	(13,241)
Net cash paid to vendors, employees and others	(168,036)	(182,568)	(171,998)
Income taxes	(73,633)	(69,341)	(48,876)
Payments to FDIC, loss share agreement	0	0	(64)
Net cash provided by operating activities	185,096	208,182	164,953
Cash Flows from Investing Activities
Proceeds from redemption of FHLB stock	0	0	17,250
Net change in interest-earning balances from depository institutions	(40,632)	4,739	13,076
Proceeds from sale of investment securities held-for-sale	0	152,644	716,996
Proceeds from repayment of investment securities available-for-sale	642,576	364,126	383,155
Proceeds from maturity of investment securities available-for-sale	9,807	7,109	24,651
Purchases of investment securities available-for-sale	(1,231,163)	(492,995)	(98,709)
Proceeds from repayment and maturity of investment securities held-to-maturity	146,309	114,569	81,816
Purchases of investment securities held-to-maturity	(52,855)	(47,587)	0
Net increase in equity investments	(3,608)	(16,488)	(24,863)
Net (increase) decrease in loan and lease finance receivables	(743,290)	231,105	(179,054)
Proceeds on eminent domain condemnation, net	0	5,685	3,425
Proceeds from sale of building, net of selling costs	2,131	5,755	0
Purchase of premises and equipment	(4,672)	(5,522)	(4,194)
Proceeds from BOLI death benefit	5,477	1,660	2,383
Proceeds from sales of other real estate owned	1,162	523	8,067
Cash acquired from acquisition, net of cash paid	0	0	(132,918)
Net cash (used in) provided by investing activities	(1,268,758)	325,323	811,081
Cash Flows from Financing Activities
Net increase (decrease) in other deposits	3,076,187	(36,926)	(444,316)
Net decrease in time deposits	(44,614)	(85,636)	(145,033)
Repayment of FHLB advances	0	0	(297,571)
Net increase (decrease) in other borrowings	5,000	(280,000)	114,000
Net increase (decrease) in customer repurchase agreements	10,747	(13,596)	(111,518)
Cash dividends on common stock	(98,475)	(95,352)	(65,966)
Repurchase of common stock	(92,772)	(2,640)	(7,760)
Proceeds from exercise of stock options	231	2,215	1,701
Net cash provided by (used in) financing activities	2,856,304	(511,935)	(956,463)
Net increase in cash and cash equivalents	1,772,642	21,570	19,571
Cash and cash equivalents, beginning of period	185,518	163,948	144,377
Cash and cash equivalents, end of period	1,958,160	185,518	163,948
Reconciliation of Net Earnings to Net Cash Provided by Operating Activities
Net earnings	177,159	207,827	152,003
Adjustments to reconcile net earnings to net cash provided by operating activities:
Gain on sale of investment securities, net	0	(5)	0
Gain on eminent domain condemnation, net	0	(5,685)	0
Gain on sale of building, net	(1,680)	(4,776)	0
Gain on sale of other real estate owned	(365)	(105)	(3,540)
Increase in BOLI	(5,303)	(5,670)	(5,751)
Net amortization of premiums and discounts on investment securities	15,045	10,298	13,531
Accretion of discount for acquired loans, net	(17,412)	(28,831)	(15,400)
Provision for credit losses	23,500	5,000	1,500
Recapture of provision for unfunded loan commitments	0	0	(250)
Valuation allowance on other real estate owned	700	0	0
Payments to FDIC, loss share agreement	0	0	(64)
Stock-based compensation	5,529	5,548	3,508
Depreciation and amortization, net	(1,157)	22,036	8,349
Change in other assets and liabilities	(10,920)	2,545	11,067
Total adjustments	7,937	355	12,950
Net cash provided by operating activities	185,096	208,182	164,953
Supplemental Disclosure of Non-cash Investing Activities
Securities purchased and not settled	60,113	0	0
Transfer of loans to other real estate owned	0	4,889	420
Issuance of common stock for acquisition	$ 0	$ 0	$ 722,767