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Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) | Dec. 31, 2020 | Dec. 31, 2019
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | $ 39,396,000 | $ 9,181,000
U.S. government and federal agency obligations |  | 838,059,000 | 851,776,000
Government-sponsored enterprise obligations |  | 54,485,000 | 139,277,000
State and municipal obligations |  | 2,045,099,000 | 1,267,927,000
Agency mortgage-backed securities |  | 6,712,085,000 | 3,937,964,000
Non-agency mortgage-backed securities |  | 361,074,000 | 809,782,000
Asset-backed securities |  | 1,882,243,000 | 1,233,489,000
Other debt securities |  | 556,219,000 | 331,411,000
Trading securities |  | 35,321,000 | 28,161,000
Equity securities with readily determinable fair values |  | 2,966,000 | 2,929,000
Private equity investments |  | 94,368,000 | 94,122,000
Derivative Assets | [1] | 89,889,000 | 105,674,000
Deferred Compensation Plan Assets |  | 19,278,000 | 16,518,000
Total Assets |  | 12,730,482,000 | 8,828,211,000
Derivative Liability | [1] | 18,675,000 | 10,219,000
Deferred Compensation Liability, Current and Noncurrent |  | 19,278,000 | 16,518,000
Total liabilities |  | 37,953,000 | 26,737,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | 0 | 0
U.S. government and federal agency obligations |  | 838,059,000 | 851,776,000
Government-sponsored enterprise obligations |  | 0 | 0
State and municipal obligations |  | 0 | 0
Agency mortgage-backed securities |  | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Other debt securities |  | 0 | 0
Trading securities |  | 0 | 0
Equity securities with readily determinable fair values |  | 2,966,000 | 2,929,000
Private equity investments |  | 0 | 0
Derivative Assets | [1] | 0 | 0
Deferred Compensation Plan Assets |  | 19,278,000 | 16,518,000
Total Assets |  | 860,303,000 | 871,223,000
Derivative Liability | [1] | 0 | 0
Deferred Compensation Liability, Current and Noncurrent |  | 19,278,000 | 16,518,000
Total liabilities |  | 19,278,000 | 16,518,000
Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | 39,396,000 | 9,181,000
U.S. government and federal agency obligations |  | 0 | 0
Government-sponsored enterprise obligations |  | 54,485,000 | 139,277,000
State and municipal obligations |  | 2,037,131,000 | 1,258,074,000
Agency mortgage-backed securities |  | 6,712,085,000 | 3,937,964,000
Non-agency mortgage-backed securities |  | 361,074,000 | 809,782,000
Asset-backed securities |  | 1,882,243,000 | 1,233,489,000
Other debt securities |  | 556,219,000 | 331,411,000
Trading securities |  | 35,321,000 | 28,161,000
Equity securities with readily determinable fair values |  | 0 | 0
Private equity investments |  | 0 | 0
Derivative Assets | [1] | 86,447,000 | 105,075,000
Deferred Compensation Plan Assets |  | 0 | 0
Total Assets |  | 11,764,401,000 | 7,852,414,000
Derivative Liability | [1] | 17,974,000 | 9,989,000
Deferred Compensation Liability, Current and Noncurrent |  | 0 | 0
Total liabilities |  | 17,974,000 | 9,989,000
Significant Unobservable Inputs (Level 3) [Member] |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |
Mortgages Held-for-sale, Fair Value Disclosure |  | 0 | 0
U.S. government and federal agency obligations |  | 0 | 0
Government-sponsored enterprise obligations |  | 0 | 0
State and municipal obligations |  | 7,968,000 | 9,853,000
Agency mortgage-backed securities |  | 0 | 0
Non-agency mortgage-backed securities |  | 0 | 0
Asset-backed securities |  | 0 | 0
Other debt securities |  | 0 | 0
Trading securities |  | 0 | 0
Equity securities with readily determinable fair values |  | 0 | 0
Private equity investments |  | 94,368,000 | 94,122,000
Derivative Assets | [1] | 3,442,000 | 599,000
Deferred Compensation Plan Assets |  | 0 | 0
Total Assets |  | 105,778,000 | 104,574,000
Derivative Liability | [1] | 701,000 | 230,000
Deferred Compensation Liability, Current and Noncurrent |  | 0 | 0
Total liabilities |  | $ 701,000 | $ 230,000
[1] | The fair value of each class of derivative is shown in Note 19.

X
- Definition The fair value as of the balance sheet date of firm holdings in Agency mortgage-backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the agency mortgage-backed security). + References No definition available. + Details
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- Definition The fair value as of the balance sheet date of firm holdings in non-agency mortgage-backed securities (investment instruments that represent ownership of an undivided interest in a group of mortgages, where principal and interest from the individual mortgages are used to pay investors' principal and interest on the non-agency mortgage-backed security). + References No definition available. + Details
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- Definition The fair value as of balance sheet date of firm holdings in debt securities which are not otherwise provided for in the existing taxonomy in the form of individual elements. + References No definition available. + Details
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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details
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- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The fair value as of the balance sheet date of firm holdings in private equity, mezzanine, venture capital, merchant banking, real estate and special situations investments. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
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- Definition The fair value as of the balance sheet date of firm holdings in fixed income obligations issued by state and local governments and authorities. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
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- Definition The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35711157&loc=d3e42546-110969 + Details
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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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