Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 352,419	$ 376,719
Overnight investments	3,137,945	1,107,844
Debt Securities, Available-for-sale	9,019,788	7,059,674
Investment securities held to maturity at cost	747,732	30,996
Investment in marketable equity securities	93,074	82,333
Loans held for sale	120,300	67,900
Loans and Leases Receivable, Net Amount	32,621,208	28,656,355
Income earned not collected	151,737	123,154
Stock issued by Federal Home Loan Bank	45,400	43,000
Deposits	42,250,606	34,431,236
Securities sold under customer repurchase agreements	693,889	442,956
FDIC shared-loss payable	15,313	112,395
Subordinated Debt	504,381	163,412
Other Borrowings	92,456	148,318
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	655,179	572,185
Cash and due from banks	352,419	376,719
Overnight investments	3,137,945	1,107,844
Debt Securities, Available-for-sale	9,019,788	7,059,674
Investment securities held to maturity at cost	747,732	30,996
Investment in marketable equity securities	93,074	82,333
Loans held for sale	120,305	67,869
Loans and Leases Receivable, Net Amount	32,621,208	28,656,355
Income earned not collected	151,737	123,154
Stock issued by Federal Home Loan Bank	45,392	43,039
Mortgage servicing rights	19,484	24,891
Deposits	39,110,297	30,593,627
Time deposits	3,140,309	3,837,609
Securities sold under customer repurchase agreements	693,889	442,956
FDIC shared-loss payable	15,313	112,395
Accrued interest payable	10,477	18,124
Subordinated Debt	504,381	163,412
Other Borrowings	92,456	148,318
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Home Loan Bank Advances	680,718	577,362
Cash and due from banks	352,419	376,719
Overnight investments	3,137,945	1,107,844
Debt Securities, Available-for-sale	9,019,788	7,059,674
Investment securities held to maturity at cost	761,252	30,996
Investment in marketable equity securities	93,074	82,333
Loans held for sale	120,305	67,869
Loans and Leases Receivable, Net Amount	33,269,733	28,878,550
Income earned not collected	151,737	123,154
Stock issued by Federal Home Loan Bank	45,392	43,039
Mortgage servicing rights	20,313	26,927
Deposits	39,110,297	30,593,627
Time deposits	3,162,058	3,842,162
Securities sold under customer repurchase agreements	693,889	442,956
FDIC shared-loss payable	15,789	114,252
Accrued interest payable	10,477	18,124
Subordinated Debt	509,518	173,685
Other Borrowings	$ 92,794	$ 149,232