Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities:
Net income	$ 116,015	$ 54,753
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	63	175,197
Deferred tax expense (benefit)	4,172	(26,089)
Accretion of loan discounts	(3,425)	(4,060)
Securities premium amortization (discount accretion), net	30,598	31,760
Net (gain) loss on securities transactions	0	(108,989)
Depreciation and amortization	16,941	15,518
Net (gain) loss on sale/write-down of assets/foreclosed assets	(134)	397
Stock-based compensation	2,526	2,512
Net tax benefit from stock-based compensation	3,136	336
Earnings on life insurance policies	(740)	(922)
Net change in:
Trading account securities	(2,153)	(12,819)
Lease right-of-use assets	5,889	5,620
Accrued interest receivable and other assets	73,164	(81,100)
Accrued interest payable and other liabilities	(26,287)	196,814
Net cash from operating activities	219,765	248,928
Investing Activities:
Securities held-to-maturity - Purchases	0	(1,500)
Securities held to maturity: Maturities, calls and principal repayments	120,029	41,526
Securities available for sale:
Purchases	(455,091)	(687,759)
Sales	0	1,111,102
Maturities, calls and principal repayments	351,612	581,882
Proceeds from sale of loans	0	0
Net change in loans	(406,836)	(622,514)
Benefits received on life insurance policies	968	0
Proceeds from sales of premises and equipment	3	1
Purchases of premises and equipment	(12,814)	(31,749)
Proceeds from sales of repossessed properties	100	8
Net cash from investing activities	(402,029)	390,997
Financing Activities:
Net change in deposits	1,909,419	501,303
Net change in short-term borrowings	(193,573)	(524,364)
Redemption of Series A preferred stock	0	(150,000)
Proceeds from stock option exercises	29,397	1,463
Purchase of treasury stock	(1,288)	(13,973)
Cash dividends paid on preferred stock	(2,151)	(2,016)
Cash dividends paid on common stock	(46,124)	(44,934)
Net cash from financing activities	1,695,680	(232,521)
Net change in cash and cash equivalents	1,513,416	407,404
Cash and cash equivalent at beginning of period	10,288,853	3,788,181
Cash and cash equivalents at end of period	$ 11,802,269	$ 4,195,585