Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Held to maturity securities	$ 2,727,945	$ 2,852,495
Loans held for sale	13,298	10,843
Derivative assets	127,529	110,734
Derivative liabilities	122,171	32,601
Total Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,359,300	888,519
Available for sale securities	5,188,156	5,556,041
Held to maturity securities	2,430,287	2,615,398
Loans, net	23,076,015	22,137,375
Loans held for sale	15,862	26,385
Derivative assets	124,431	109,497
Deposits	30,298,620	29,041,635
Federal funds purchased	350	1,850
Securities sold under agreements to repurchase	525,578	444,421
FHLB short-term borrowings	899,995	1,425,000
Long-term debt	183,901	200,060
Derivative liabilities	307,669	204,121
Total Fair Value [Member] | Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,359,300	888,519
Federal funds purchased	350	1,850
Securities sold under agreements to repurchase	525,578	444,421
FHLB short-term borrowings		1,425,000
Total Fair Value [Member] | Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available for sale securities	5,188,156	5,556,041
Held to maturity securities	2,430,287	2,615,398
Loans, net	17,658	4,692
Loans held for sale	15,862	26,385
Derivative assets	124,431	109,497
FHLB short-term borrowings	899,995
Long-term debt	183,901	200,060
Derivative liabilities	306,237	202,238
Total Fair Value [Member] | Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Loans, net	23,058,357	22,132,683
Deposits	30,298,620	29,041,635
Derivative liabilities	1,432	1,883
Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash, interest-bearing bank deposits, and federal funds sold	1,359,300	888,519
Available for sale securities	5,188,156	5,556,041
Held to maturity securities	2,727,945	2,852,495
Loans, net	23,677,388	22,806,257
Loans held for sale	15,862	26,385
Derivative assets	124,431	109,497
Deposits	30,320,337	29,070,349
Federal funds purchased	350	1,850
Securities sold under agreements to repurchase	525,578	444,421
FHLB short-term borrowings	900,000	1,425,000
Long-term debt	236,279	242,077
Derivative liabilities	$ 307,669	$ 204,121