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Organization, Business and Summary of Significant Accounting Policies (Company's Derivative Instruments of Fuel Hedge Agreements) (Detail) (Fuel [Member], Commodity Contract [Member])
 12 Months Ended
Dec. 31, 2014
Fuel [Member] | Commodity Contract [Member]
  
Derivative [Line Items]  
Date entered 2012-06
Notional amount (in gallons per month) 300,000invest_DerivativeNonmonetaryNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
/ us-gaap_EnergyAxis
= us-gaap_FuelMember
Diesel rate paid fixed (per gallon) 3.60us-gaap_DerivativeForwardPrice
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
/ us-gaap_EnergyAxis
= us-gaap_FuelMember
Diesel rate received variable DOE Diesel Fuel Index* [1]
Effective date 2014-01
Expiration date 2015-12
[1] If the national U.S. on-highway average price for a gallon of diesel fuel (“average price”), as published by the Department of Energy, exceeds the contract price per gallon, the Company receives the difference between the average price and the contract price (multiplied by the notional number of gallons) from the counterparty.  If the average price is less than the contract price per gallon, the Company pays the difference to the counterparty.