Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 410,495	$ 362,048
Overnight investments	7,588,757	4,347,336
Debt Securities, Available-for-sale	7,307,122	7,014,243
Investment securities held to maturity at cost	2,808,099	2,816,982
Investment in marketable equity securities	106,886	91,680
Loans held for sale	129,300	124,800
Loans and Leases Receivable, Net Amount	32,970,200	32,567,661
Income earned not collected	148,022	145,694
Stock issued by Federal Home Loan Bank	40,600	45,400
Deposits	47,330,997	43,431,609
Securities sold under customer repurchase agreements	680,705	641,487
FDIC shared-loss payable	0	15,601
Subordinated Debt	497,153	504,518
Other Borrowings	84,502	88,470
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	648,671	655,175
Cash and due from banks	410,495	362,048
Overnight investments	7,588,757	4,347,336
Debt Securities, Available-for-sale	7,307,122	7,014,243
Investment securities held to maturity at cost	2,808,099	2,816,982
Investment in marketable equity securities	106,886	91,680
Loans held for sale	129,334	124,837
Loans and Leases Receivable, Net Amount	32,970,200	32,567,661
Income earned not collected	148,022	145,694
Stock issued by Federal Home Loan Bank	40,563	45,392
Mortgage servicing rights	23,728	19,628
Deposits	44,601,552	40,542,596
Time deposits	2,729,445	2,889,013
Securities sold under customer repurchase agreements	680,705	641,487
FDIC shared-loss payable	0	15,601
Accrued interest payable	5,149	9,414
Subordinated Debt	497,153	504,518
Other Borrowings	84,502	88,470
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	664,996	677,579
Cash and due from banks	410,495	362,048
Overnight investments	7,588,757	4,347,336
Debt Securities, Available-for-sale	7,307,122	7,014,243
Investment securities held to maturity at cost	2,774,982	2,838,499
Investment in marketable equity securities	106,886	91,680
Loans held for sale	129,334	124,837
Loans and Leases Receivable, Net Amount	33,202,437	33,298,166
Income earned not collected	148,022	145,694
Stock issued by Federal Home Loan Bank	40,563	45,392
Mortgage servicing rights	24,322	20,283
Deposits	44,601,552	40,542,596
Time deposits	2,738,244	2,905,577
Securities sold under customer repurchase agreements	680,705	641,487
FDIC shared-loss payable	0	15,843
Accrued interest payable	5,149	9,414
Subordinated Debt	517,091	525,610
Other Borrowings	$ 85,067	$ 89,263

Payable to FDIC for Loss Share Agreements

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of Federal Home Loan Bank (FHLBank) advances to member financial institutions.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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