Commitments and Contingencies (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments and Contingencies [Line Items]
Purchase Commitments Physical Commodity Requirements Utilization Period	3 years
Unrecorded Unconditional Purchase Obligation, Total	$ 677,652
2020	240,832
2021	118,613
Capital Addition Purchase Commitments [Member]
Commitments and Contingencies [Line Items]
Unrecorded Unconditional Purchase Obligation, Total	820,400
2020	734,000
2021	$ 86,400
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	13 years