Significant Accounting Policies (Property Plant and Equipment & Intangible Assets) (Details)	12 Months Ended
Dec. 31, 2014
Building and building improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful life	40 years
Building and building improvements \| NACoal
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful life	30 years
Machinery and equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful life	3 years
Machinery and equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment useful life	15 years

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

No definition available.

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration