Derivatives (Narrative) (Details) gal in Millions	3 Months Ended
Mar. 31, 2016 gal
Diesel swap
Derivative [Line Items]
Fixed price swap contract (in gallons)	9.7

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration