Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 337,450	$ 362,048
Debt Securities, Available-for-sale	7,371,129	7,014,243
Investment securities held to maturity at cost	3,381,078	2,816,982
Investment in marketable equity securities	123,147	91,680
Loans held for sale	98,500	124,800
Loans and Leases Receivable, Net Amount	32,332,995	32,567,661
Income earned not collected	132,911	145,694
Stock issued by Federal Home Loan Bank	40,500	45,400
Deposits	50,065,762	43,431,609
Securities sold under customer repurchase agreements	663,575	641,487
FDIC shared-loss payable	0	15,601
Subordinated Debt	497,427	504,518
Other Borrowings	76,139	88,470
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	645,663	655,175
Cash and due from banks	337,450	362,048
Overnight investments	9,875,063	4,347,336
Debt Securities, Available-for-sale	7,371,129	7,014,243
Investment securities held to maturity at cost	3,381,078	2,816,982
Investment in marketable equity securities	123,147	91,680
Loans held for sale	98,451	124,837
Loans and Leases Receivable, Net Amount	32,332,995	32,567,661
Income earned not collected	132,911	145,694
Stock issued by Federal Home Loan Bank	40,450	45,392
Mortgage servicing rights	22,263	19,628
Deposits	47,492,194	40,542,596
Time deposits	2,573,568	2,889,013
Securities sold under customer repurchase agreements	663,575	641,487
FDIC shared-loss payable	0	15,601
Accrued interest payable	6,560	9,414
Subordinated Debt	497,427	504,518
Other Borrowings	76,139	88,470
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	659,625	677,579
Cash and due from banks	337,450	362,048
Overnight investments	9,875,063	4,347,336
Debt Securities, Available-for-sale	7,371,129	7,014,243
Investment securities held to maturity at cost	3,353,078	2,838,499
Investment in marketable equity securities	123,147	91,680
Loans held for sale	98,451	124,837
Loans and Leases Receivable, Net Amount	32,349,172	33,298,166
Income earned not collected	132,911	145,694
Stock issued by Federal Home Loan Bank	40,450	45,392
Mortgage servicing rights	22,624	20,283
Deposits	47,492,194	40,542,596
Time deposits	2,573,131	2,905,577
Securities sold under customer repurchase agreements	663,575	641,487
FDIC shared-loss payable	0	15,843
Accrued interest payable	6,560	9,414
Subordinated Debt	520,871	525,610
Other Borrowings	$ 76,643	$ 89,263