Significant Accounting Policies and Methods of Application - Estimated Useful Lives of Assets (Details)	12 Months Ended
	Dec. 31, 2015
Transportation equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Transportation equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	10 years
Storage Caverns [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years
Storage Caverns [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	60 years
Other [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	40 years