Income Taxes (Narrative) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Federal statutory income tax rate, percent			21.00%	35.00%
Tax benefit from change in enacted tax rate	[1]	$ 0	$ 0	$ (81,307,000)
Income tax benefit		(132,326,000)	(13,996,000)	(57,678,000)
Goodwill impairment		62,800,000	0	0
Nondeductible expense from goodwill impairment		50,300,000
Deductible expense from goodwill impairment		$ 12,346,000	0	$ 0
Valuation Allowance, Commentary		During the year ended December 31, 2019, in evaluating whether it was more likely than not that the company's deferred tax assets were realizable through future net income, we considered all available positive and negative evidence, including (i) our earnings history exclusive of the loss that created the future deductible amount coupled with evidence indicating that the loss is an aberration rather than a continuing condition, (ii) our ability to recover net operating loss carryforward deferred tax assets in future years, (iii) the existence of significant proved oil, NGL and natural gas reserves, (iv) future revenue and operating cost projections that indicate the company will produce more than enough taxable income to realize the deferred tax asset based on existing sales prices and cost structures and (vii) current market prices for oil, NGL and natural gas. Based on all the evidence available, we determined it was more likely than not that the deferred tax asset for net operating loss carryforwards were not fully realizable. As of December 31, 2019, a total valuation allowance of $19.7 million has been recorded.
Valuation allowance		$ (19,654,000)	$ 0
Operating loss carryforwards		980,800,000
Operating loss carryforwards subject to expiration		$ 584,200,000
Operating loss carryforwards expiration		expire from 2021 to 2037

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