Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets:
Derivative financial instruments	$ 0	$ 0
Liabilities:
Derivative financial instruments	45	487
Fair Value, Measurements, Recurring
Investments:
Cash surrender value of life insurance policies - deferred compensation plan	31,306	30,351
Liabilities:
Derivative financial instruments	45	487
Fair Value, Measurements, Recurring \| Deferred compensation plan
Liabilities:
Deferred compensation plan	25,970	26,797
Fair Value, Measurements, Recurring \| Marketable securities - other
Investments:
Marketable securities - other	54	113
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1)
Investments:
Cash surrender value of life insurance policies - deferred compensation plan	0	0
Liabilities:
Derivative financial instruments	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Deferred compensation plan
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets (Level 1) \| Marketable securities - other
Investments:
Marketable securities - other	54	113
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Investments:
Cash surrender value of life insurance policies - deferred compensation plan	31,306	30,351
Liabilities:
Derivative financial instruments	45	487
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Deferred compensation plan
Liabilities:
Deferred compensation plan	25,970	26,797
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2) \| Marketable securities - other
Investments:
Marketable securities - other	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Investments:
Cash surrender value of life insurance policies - deferred compensation plan	0	0
Liabilities:
Derivative financial instruments	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Deferred compensation plan
Liabilities:
Deferred compensation plan	0	0
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3) \| Marketable securities - other
Investments:
Marketable securities - other	$ 0	$ 0

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Fair value portion of the amount that could be realized under a life insurance contract or contracts owned by the entity, commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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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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Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

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Amount of investment in marketable security.

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