Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities:
Net income	$ 342,058	$ 242,881
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	63	227,474
Deferred tax expense (benefit)	4,672	(8,803)
Accretion of loan discounts	(9,879)	(11,905)
Securities premium amortization (discount accretion), net	90,017	93,080
Net (gain) loss on securities transactions	0	(108,989)
Depreciation and amortization	51,550	47,752
Net (gain) loss on sale/write-down of assets/foreclosed assets	(1,885)	(6)
Stock-based compensation	7,756	8,227
Net tax benefit from stock-based compensation	4,505	694
Earnings on life insurance policies	(1,901)	(2,895)
Net change in:
Trading account securities	(421)	(197)
Lease right-of-use assets	17,566	17,419
Accrued interest receivable and other assets	(65,849)	(52,842)
Accrued interest payable and other liabilities	114,361	23,208
Net cash from operating activities	552,613	475,098
Investing Activities:
Securities held-to-maturity - Purchases	0	(1,500)
Securities held to maturity: Maturities, calls and principal repayments	171,969	63,333
Securities available for sale:
Purchases	4,105,085	8,324,364
Sales	0	1,162,352
Maturities, calls and principal repayments	3,125,786	8,162,036
Net change in loans	1,649,429	(3,551,650)
Benefits received on life insurance policies	1,944	903
Proceeds from sales of premises and equipment	7,033	3,054
Purchases of premises and equipment	(37,088)	(81,866)
Proceeds from sales of repossessed properties	809	73
Net cash from investing activities	814,797	(2,567,629)
Financing Activities:
Net change in deposits	4,597,006	5,859,939
Net change in short-term borrowings	110,232	(86,675)
Proceeds from Federal Home Loan Bank advances	0	1,250,000
Principal payments on Federal Home Loan Bank advances	0	(1,250,000)
Redemption of Series A preferred stock	0	(150,000)
Proceeds from stock option exercises	37,810	7,544
Purchase of treasury stock	(1,342)	(14,000)
Cash dividends paid on preferred stock	(5,488)	(2,016)
Cash dividends paid on common stock	(140,510)	(134,762)
Net cash from financing activities	4,597,708	5,480,030
Net change in cash and cash equivalents	5,965,118	3,387,499
Cash and cash equivalent at beginning of period	10,288,853	3,788,181
Cash and cash equivalents at end of period	$ 16,253,971	$ 7,175,680