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Fair Value Measurement - Summary of Long Term Restricted Marketable Securities Component and Workers' Compensation Deposits (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Cost $ 5,903 $ 9,870
Available-for-sale Securities [Member]
    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Cost 10,012 8,735
Gross Unrealized Gains 14 22
Recorded Basis 10,026 8,757
Available-for-sale Securities [Member] | Long-term Available-for-Sale [Member] | Municipal bonds [Member]
    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Cost 4,855 4,920
Gross Unrealized Gains 8 17
Recorded Basis 4,863 4,937
Fair Value Category   2
Available-for-sale Securities [Member] | Long-term Available-for-Sale [Member] | Corporate bonds [Member]
    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Cost 2,685 2,035
Gross Unrealized Gains 6 5
Recorded Basis 2,691 2,040
Fair Value Category   2
Available-for-sale Securities [Member] | Long-term Available-for-Sale [Member] | U.S. treasuries [Member]
    
Fair Value Inputs, Assets, Quantitative Information [Line Items]    
Cost 2,472 1,780
Gross Unrealized Gains 0 0
Recorded Basis $ 2,472 $ 1,780
Fair Value Category   1