Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net income	$ 443,079	$ 331,151	$ 443,599
Adjustments to reconcile net income to net cash from operating activities:
Credit loss expense	63	241,230	33,759
Deferred tax expense (benefit)	7,784	(15,832)	7,614
Accretion of loan discounts	(12,890)	(15,692)	(15,197)
Securities premium amortization (discount accretion), net	119,242	123,785	115,558
Net (gain) loss on securities transactions	(69)	(108,989)	(293)
Depreciation and amortization	69,289	64,370	54,091
Net (gain) loss on sale/exchange/write-down of assets/foreclosed assets	(11,578)	524	(5,712)
Stock-based compensation	12,753	13,918	15,946
Net tax benefit from stock-based compensation	7,877	852	2,447
Earnings on life insurance policies	(2,462)	(3,731)	(3,683)
Net change in:
Trading account securities	(560)	(158)	(212)
Lease right-of-use assets	23,504	23,933	20,124
Accrued interest receivable and other assets	(46,560)	(158,264)	(15,570)
Accrued interest payable and other liabilities	38,821	27,146	(18,381)
Net cash provided by (used in) operating activities	648,293	524,243	634,090
Investing Activities:
Securities held to maturity: Purchases	0	(1,500)	(649,326)
Securities held to maturity: Maturities, calls and principal repayments	177,593	63,577	81,762
Securities available for sale:
Purchases	(24,217,841)	(20,841,622)	(23,306,694)
Sales	1,999,891	1,162,352	18,660,147
Maturities, calls and principal repayments	18,425,108	20,893,464	4,694,927
Proceeds from sale of loans	0	37,535	24,036
Net change in loans	1,145,924	(2,856,395)	(693,587)
Benefits received on life insurance policies	2,307	903	0
Proceeds from sales of premises and equipment	7,044	5,988	8,038
Purchases of premises and equipment	(65,850)	(95,422)	(206,716)
Proceeds from sales of repossessed properties	809	73	663
Net cash provided by (used in) investing activities	(2,525,015)	(1,631,047)	(1,386,750)
Financing Activities:
Net change in deposits	7,679,935	7,376,197	490,360
Net change in short-term borrowings	649,727	421,655	327,794
Proceeds from Federal Home Loan Bank advances	0	1,250,000	0
Principal payments on Federal Home Loan Bank advances	0	(1,250,000)	0
Principal payments on long-term borrowings	(13,403)
Redemption of Series A preferred stock	0	(150,000)	0
Proceeds from issuance of Series B preferred stock	0	145,452	0
Proceeds from stock option exercises	54,417	12,557	20,770
Purchase of treasury stock	(3,864)	(15,785)	(68,793)
Cash dividends paid on preferred stock	(7,157)	(2,016)	(8,063)
Cash dividends paid on common stock	(188,786)	(180,584)	(177,006)
Net cash provided by (used in) financing activities	8,170,869	7,607,476	585,062
Net change in cash and cash equivalents	6,294,147	6,500,672	(167,598)
Cash and cash equivalents at beginning of year	10,288,853	3,788,181	3,955,779
Cash and cash equivalents at end of year	$ 16,583,000	$ 10,288,853	$ 3,788,181