Commitments and Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Commitments and Contingencie [Line Items]
Construction in Progress Expenditures Incurred but Not yet Paid	$ 74.7
Inventories [Member]
Commitments and Contingencie [Line Items]
Purchase Commitments Physical Commodity Requirements Utilization Period	3 years
Inventories [Member] | Maximum
Commitments and Contingencie [Line Items]
Purchase Commitments Commodity Transportation Requirements Period	5 years
Purchase Commitments Commodity Transportation Requirements Period For Products	11 years