Fair Value Measurements (Narrative) (Details) - Diesel swap gal in Millions	3 Months Ended
Mar. 31, 2016 $ / gal gal
Derivatives, Fair Value [Line Items]
Fixed price swap contract (in gallons) \| gal	9.7
Average contract price (in dollars per gallon)	2.79
Average forward price (in dollars per gallon)	2.30

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