Commitments and Contingencies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Commitments and Contingencies [Line Items]
Purchase Commitments Physical Commodity Requirements Utilization Period	3 years
Unrecorded Unconditional Purchase Obligation, Total	$ 624,809
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation, Total	$ 561,100
Maximum | Physical Commodity and Commodity Transportation [Member]
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment, Period	5 years
Maximum | Air Products [Member]
Commitments and Contingencies [Line Items]
Long-term Purchase Commitment, Period	12 years