Discontinued Operation (Cash Flow Of Discontinued Operations) (Details) - Pumpco [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation and amortization		$ 75,077	$ 122,409
Reduction in value of assets	$ 114,213	76,577	417,011
Payments for capital expenditures		(36,743)	$ (108,094)
Proceeds from sales of assets	$ 19,030	$ 1,669