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Valuation and Qualifying Accounts and Reserves (Detail) - Valuation and Qualifying Accounts and Reserves (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Insurance and Claims Accruals [Member]
      
Balance at Beginning of Year $ 13,042 $ 17,653 $ 19,222
Charged to Costs and Expenses 32,548 27,675 24,892
Deductions (31,752) [1] (32,286) [1] (26,461) [1]
Balance at End of Year 13,838 13,042 17,653
Allowance for Doubtful Accounts [Member]
      
Balance at Beginning of Year 470 170 245
Charged to Costs and Expenses   544 (21)
Deductions (136) [2] (244) [2] (54) [2]
Balance at End of Year $ 334 $ 470 $ 170
[1] Claims payments
[2] Write-off of bad debts, net of recoveries