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Assets and Liabilities Measured at Fair Value and Related Hierarchy Levels (Detail) (USD $)
In Thousands, unless otherwise specified |
Sep. 30, 2013
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Dec. 31, 2012
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|---|---|---|---|---|---|---|---|---|---|---|
| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | $ 16,208 | $ 16,350 | ||||||||
| Executive deferred compensation plan trust | 4,048 | [1] | 2,921 | [1] | ||||||
| Total fuel price derivatives - liabilities | 1,729 | |||||||||
| Contingent consideration | 313 | [2] | ||||||||
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Mortgage-backed securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 867 | 1,839 | ||||||||
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Asset-backed securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 1,490 | 1,654 | ||||||||
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Municipal bonds
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 535 | 641 | ||||||||
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Equity securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 13,316 | 12,216 | ||||||||
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Fuel price derivatives - unleaded fuel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - assets | 22 | [3] | ||||||||
| Total fuel price derivatives - liabilities | 1,622 | [3] | ||||||||
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Fuel price derivatives - diesel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - liabilities | 517 | [3] | 107 | [3] | ||||||
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Quoted Prices in Active Markets for Identical Assets (Level 1)
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 13,316 | 12,216 | ||||||||
| Executive deferred compensation plan trust | 4,048 | [1] | 2,921 | [1] | ||||||
| Contingent consideration | 0 | [2] | ||||||||
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Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 13,316 | 12,216 | ||||||||
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Quoted Prices in Active Markets for Identical Assets (Level 1) | Fuel price derivatives - unleaded fuel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - assets | 0 | [3] | ||||||||
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Quoted Prices in Active Markets for Identical Assets (Level 1) | Fuel price derivatives - diesel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - liabilities | 0 | [3] | ||||||||
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Significant Other Observable Inputs (Level 2)
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 2,892 | 4,134 | ||||||||
| Total fuel price derivatives - liabilities | 1,622 | |||||||||
| Contingent consideration | 0 | [2] | ||||||||
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Significant Other Observable Inputs (Level 2) | Mortgage-backed securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 867 | 1,839 | ||||||||
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Significant Other Observable Inputs (Level 2) | Asset-backed securities
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 1,490 | 1,654 | ||||||||
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Significant Other Observable Inputs (Level 2) | Municipal bonds
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| Fair Value Measurements [Line Items] | ||||||||||
| Total available-for-sale securities | 535 | 641 | ||||||||
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Significant Other Observable Inputs (Level 2) | Fuel price derivatives - unleaded fuel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - assets | 22 | [3] | ||||||||
| Total fuel price derivatives - liabilities | 1,622 | [3] | ||||||||
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Significant Other Observable Inputs (Level 2) | Fuel price derivatives - diesel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - liabilities | 0 | [3] | ||||||||
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Significant Other Observable Inputs (Level 3)
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - liabilities | 107 | |||||||||
| Contingent consideration | 313 | [2] | ||||||||
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Significant Other Observable Inputs (Level 3) | Fuel price derivatives - unleaded fuel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - assets | 0 | [3] | ||||||||
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Significant Other Observable Inputs (Level 3) | Fuel price derivatives - diesel
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| Fair Value Measurements [Line Items] | ||||||||||
| Total fuel price derivatives - liabilities | $ 517 | [3] | $ 107 | [3] | ||||||
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