Income Taxes (Reconciliation Of Income Tax Expense (Benefit)) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit) computed by applying the statutory rate		$ (144,092)	$ (11,290)	$ 21,059
State income tax expense (benefit), net of federal benefit		(21,733)	(1,882)	1,655
Deferred tax liability revaluation	[1]	0	0	(81,307)
Restricted stock shortfall		347	424	1,867
Non-controlling interest in Superior		(11)	(1,138)	0
Goodwill impairment		12,346	0	0
Valuation allowance		19,654	0	0
Statutory depletion and other		1,163	(110)	(952)
Income tax benefit		$ (132,326)	$ (13,996)	$ (57,678)

[1] In 2017, the revaluation from the Tax Act.