Commitments and Contingencies (Narrative) (Details)					1 Months Ended	6 Months Ended
	Jun. 15, 2021 USD ($)	Apr. 22, 2021 bbl	Jan. 14, 2015 USD ($)	Apr. 23, 2014 USD ($)	Jul. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)
Commitments And Contingencies [Line Items]
Outstanding performance bonds						$ 1,143,833,000
Revenue value remaining from outstanding performance bonds						454,402,000
Proceeds from Legal Settlements			$ 5,309,000
Fine for violation	$ 1,000,000
Subsequent Event [Member]
Commitments And Contingencies [Line Items]
Civil penalty					$ 500,000
Indemnification Commitment [Member]
Commitments And Contingencies [Line Items]
Aggregate demolition surety performance bond				$ 21,934,000
Crude Oil [Member]
Commitments And Contingencies [Line Items]
Quantity of oil spill | bbl		160
Minimum [Member]
Commitments And Contingencies [Line Items]
Bids bond range						$ 1,000,000
Warranty periods						1 year
Maximum [Member]
Commitments And Contingencies [Line Items]
Bids bond range						$ 10,000,000
Warranty periods						3 years