Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	$ 15,357us-gaap_TradingSecurities	$ 19,993us-gaap_TradingSecurities
Derivative Assets	10,457us-gaap_DerivativeAssets	12,980us-gaap_DerivativeAssets
Derivative Liabilities	10,948us-gaap_DerivativeLiabilities	13,329us-gaap_DerivativeLiabilities
Total Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	501,407	505,696
Government-sponsored enterprise obligations	963,127	741,766
State and municipal obligations	1,813,201	1,619,171
Agency mortgage-backed securities	2,593,708	2,772,338
Non-agency mortgage-backed securities	382,744	246,983
Asset-backed securities	3,091,993	2,844,071
Other debt securities	139,161	141,757
Equity securities	38,219	43,898
Trading securities	15,357	19,993
Private equity investments	57,581	56,612
Derivative Assets	10,457	12,980
Assets held in trust	8,848	7,511
Total assets	9,615,803	9,012,776
Derivative Liabilities	10,948	13,329
Total liabilities	10,948	13,329
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	501,407	505,696
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
Equity securities	17,975	24,646
Trading securities	0	0
Private equity investments	0	0
Derivative Assets	0	0
Assets held in trust	8,848	7,511
Total assets	528,230	537,853
Derivative Liabilities	0	0
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	963,127	741,766
State and municipal obligations	1,718,058	1,491,447
Agency mortgage-backed securities	2,593,708	2,772,338
Non-agency mortgage-backed securities	382,744	246,983
Asset-backed securities	3,091,993	2,844,071
Other debt securities	139,161	141,757
Equity securities	20,244	19,252
Trading securities	15,357	19,993
Private equity investments	0	0
Derivative Assets	10,454	12,976
Assets held in trust	0	0
Total assets	8,934,846	8,290,583
Derivative Liabilities	10,722	13,260
Total liabilities	10,722	13,260
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. government and federal agency obligations	0	0
Government-sponsored enterprise obligations	0	0
State and municipal obligations	95,143	127,724
Agency mortgage-backed securities	0	0
Non-agency mortgage-backed securities	0	0
Asset-backed securities	0	0
Other debt securities	0	0
Equity securities	0	0
Trading securities	0	0
Private equity investments	57,581	56,612
Derivative Assets	3	4
Assets held in trust	0	0
Total assets	152,727	184,340
Derivative Liabilities	226	69
Total liabilities	$ 226	$ 69

Assets held in an outside trust for the Company's deferred compensation plan consist of investments in mutual funds.

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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).

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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).

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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.

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Other Asset Backed Securities Disclosure

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- Definition

U S Government Sponsored Enterprises Debt Securities

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

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- Definition

Amount of investments in equity securities and other forms of securities that provide ownership interests classified as available-for-sale, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

+ References

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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.

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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.

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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.

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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.

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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.

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Fair value of financial and nonfinancial obligations.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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