Estimated Fair Values (Estimated Fair Values For Certain Financial Assets And Financial Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	$ 336,150	$ 539,741
Overnight investments	1,387,927	1,872,594
Investment securities available for sale	7,180,180	7,006,580
Investment securities held to maturity	76	98
Net loans and leases	23,374,932	21,519,083
FDIC loss share receivable	2,223	4,172	$ 4,054	$ 28,701
Income earned not collected	95,249	79,839
Deposits	29,266,275	28,161,343
Short-term borrowings	693,807	603,487
Long-term obligations	870,240	832,942
FDIC shared-loss payable	101,342	97,008
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	336,150	539,741
Overnight investments	1,387,927	1,872,594
Investment securities available for sale	7,180,180	7,006,580
Investment securities held to maturity	76	98
Loans held for sale	51,179	74,401
Net loans and leases	23,374,932	21,519,083
FDIC loss share receivable	2,223	4,172
Income earned not collected	95,249	79,839
Federal Home Loan Bank stock	52,685	43,495
Mortgage servicing assets	21,945	20,415
Deposits	29,266,275	28,161,343
Short-term borrowings	693,807	603,487
Long-term obligations	870,240	832,942
FDIC shared-loss payable	101,342	97,008
Accrued interest payable	3,952	3,797
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and due from banks	336,150	539,741
Overnight investments	1,387,927	1,872,594
Investment securities available for sale	7,180,180	7,006,580
Investment securities held to maturity	81	104
Loans held for sale	51,179	74,401
Net loans and leases	22,257,803	20,614,548
FDIC loss share receivable	2,223	4,172
Income earned not collected	95,249	79,839
Federal Home Loan Bank stock	52,685	43,495
Mortgage servicing assets	26,170	24,446
Deposits	29,230,768	28,135,698
Short-term borrowings	693,807	603,487
Long-term obligations	852,112	832,201
FDIC shared-loss payable	102,684	100,069
Accrued interest payable	$ 3,952	$ 3,797

Payable to FDIC for Loss Share Agreements

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For an unclassified balance sheet, the amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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For banks and other depository institutions: Includes cash on hand (currency and coin), cash items in process of collection, noninterest bearing deposits due from other financial institutions (including corporate credit unions), and noninterest bearing balances with the Federal Reserve Banks, Federal Home Loan Banks and central banks.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Carrying amount of receivable assets originating from the indemnification agreement with the Federal Deposit Insurance Corporation (FDIC), in which the FDIC is to partially cover losses.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of interest payable on debt, including, but not limited to, trade payables.

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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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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount of short-term investments classified as other.

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Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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