Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating Activities:
Net income	$ 234,083	$ 147,825
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	63	207,172
Deferred tax expense (benefit)	5,188	(51,933)
Accretion of loan discounts	(6,577)	(7,680)
Securities premium amortization (discount accretion), net	60,434	62,177
Net (gain) loss on securities transactions	0	(108,989)
Depreciation and amortization	34,060	31,489
Net (gain) loss on sale/write-down of assets/foreclosed assets	(1,876)	(139)
Stock-based compensation	5,771	5,784
Net tax benefit from stock-based compensation	4,218	556
Earnings on life insurance policies	(1,343)	(1,935)
Net change in:
Trading account securities	319	(197)
Lease right-of-use assets	11,697	11,491
Accrued interest receivable and other assets	(39,195)	(131,772)
Accrued interest payable and other liabilities	41,748	43,111
Net cash from operating activities	348,590	206,960
Investing Activities:
Securities held-to-maturity - Purchases	0	(1,500)
Securities held to maturity: Maturities, calls and principal repayments	122,416	51,232
Securities available for sale:
Purchases	(801,167)	(3,739,598)
Sales	0	1,162,352
Maturities, calls and principal repayments	576,763	3,791,908
Net change in loans	884,799	(3,293,619)
Benefits received on life insurance policies	1,509	0
Proceeds from sales of premises and equipment	6,436	3,054
Purchases of premises and equipment	(28,053)	(52,036)
Proceeds from sales of repossessed properties	100	8
Net cash from investing activities	762,803	(2,078,199)
Financing Activities:
Net change in deposits	3,718,379	5,039,532
Net change in short-term borrowings	126,592	(105,958)
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	36,682	4,846
Purchase of treasury stock	(1,288)	(13,973)
Cash dividends paid on preferred stock	(3,820)	(2,016)
Cash dividends paid on common stock	(92,396)	(89,805)
Net cash from financing activities	3,784,149	4,682,626
Net change in cash and cash equivalents	4,895,542	2,811,387
Cash and cash equivalent at beginning of period	10,288,853	3,788,181
Cash and cash equivalents at end of period	$ 15,184,395	$ 6,599,568