Fair Value of Postretirement Assets (Detail) (Other Benefits, USD $)
In Thousands, unless otherwise specified |
Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | $ 21,400 | $ 19,300 | $ 18,900 | |||||||||||
Large-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 4,100 | [1] | ||||||||||||
Small- and Mid-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 800 | [1] | ||||||||||||
International Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 3,600 | [1],[2] | ||||||||||||
Fixed Income
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 5,900 | [1],[2] | ||||||||||||
Private Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 1,600 | [3] | ||||||||||||
Hedge Funds
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 3,800 | [4] | ||||||||||||
Real Assets
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 1,300 | [1],[5] | ||||||||||||
Cash
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 300 | [1] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1)
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 9,400 | |||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | Large-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 4,100 | [1] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | Small- and Mid-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 800 | [1] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | International Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 2,900 | [1],[2] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed Income
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 500 | [1],[2] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | Real Assets
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 800 | [1],[5] | ||||||||||||
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 300 | [1] | ||||||||||||
Significant Other Observable Inputs (Level 2)
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 6,100 | |||||||||||||
Significant Other Observable Inputs (Level 2) | Large-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Small- and Mid-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1] | ||||||||||||
Significant Other Observable Inputs (Level 2) | International Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 700 | [1],[2] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Fixed Income
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 5,400 | [1],[2] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Private Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [3] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Hedge Funds
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [4] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Real Assets
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1],[5] | ||||||||||||
Significant Other Observable Inputs (Level 2) | Cash
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1] | ||||||||||||
Significant Unobservable Inputs (Level 3)
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 5,900 | |||||||||||||
Significant Unobservable Inputs (Level 3) | Large-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Small- and Mid-Cap Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1] | ||||||||||||
Significant Unobservable Inputs (Level 3) | International Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1],[2] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Fixed Income
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 0 | [1],[2] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Private Equity
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 1,600 | [3] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Hedge Funds
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 3,800 | [4] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Real Assets
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | 500 | [1],[5] | ||||||||||||
Significant Unobservable Inputs (Level 3) | Cash
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Defined Benefit Plan Disclosure [Line Items] | ||||||||||||||
Fair value of plan assets | $ 0 | [1] | ||||||||||||
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