Long-Term Debt And Other Long-Term Liabilities (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended
	May 02, 2018	Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest percentage of senior subordinated notes		6.625%
Debt instrument maturity date		May 15, 2021
Estimated principal payments in year 1		$ 14,300
Estimated principal payments in year 2		47,800
Estimated principal payments in year 3		656,900
Estimated principal payments in year 4		3,600
Estimated principal payments in year 5		42,300
6.625% Senior Subordinated Notes Due 2021 [Member]
Debt Instrument [Line Items]
Aggregate principal amount		$ 650,000	$ 650,000
Interest percentage of senior subordinated notes		6.625%
Debt instrument maturity date		May 15, 2021
Original debt issuance fees		$ 14,700
Senior notes repurchase price in percentage		101.00%
Unit Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility maximum credit amount		$ 1,000,000
Commitment fee percentage under credit facility		0.375%
Origination, agency and syndication and other related fees with the credit agreement		$ 3,300
Payable assessment term for LIBOR		90 days
LIBOR interest rate plus one percent		LIBOR plus 1.00% plus a margin
Line of credit facility, amount outstanding		$ 40,000	0
Unit Credit Agreement, Dividend Restrictions		the payment of dividends (other than stock dividends) during any fiscal year over 30% of our consolidated net income for the preceding fiscal year;
Unit Credit Agreement, Asset Restrictions		investments in Unrestricted Subsidiaries (as defined in the Unit credit agreement) over $200.0 million
Current ratio of credit facility		1 to 1
Leverage ratio of credit facility		4 to 1
Covenant Compliance		As of March 31, 2019, we were in compliance with these covenants.
Unit Credit Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
LIBOR plus interest rate		1.50%
Unit Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
LIBOR plus interest rate		2.50%
Unit Credit Agreement [Member] | Line Of Credit Facility Commitment Amount [Member]
Debt Instrument [Line Items]
Credit facility current credit amount		$ 425,000
Unit Credit Agreement [Member] | Line Of Credit Facility Lender Determined Amount [Member]
Debt Instrument [Line Items]
Credit facility current credit amount		$ 425,000
Unit Credit Agreement [Member] | Proved developed producing total value of our oil and gas properties [Member]
Debt Instrument [Line Items]
Percentage of collateral pledged		80.00%
Present worth discounted		8.00%
Superior Credit Agreement [Member]
Debt Instrument [Line Items]
Credit facility maximum credit amount		$ 250,000
Credit facility current credit amount		$ 200,000
Commitment fee percentage under credit facility		0.375%
Origination, agency and syndication and other related fees with the credit agreement		$ 1,700
Line of credit facility, amount outstanding		$ 0	$ 0
Covenant Compliance		As of March 31, 2019, Superior was in compliance with these covenants.
Superior Credit Agreement, Term		5 years
Superior Credit Agreement, Interest Rate Description		annual interest at a rate, at Superior’s option, equal to (a) LIBOR plus the applicable margin of 2.00% to 3.25% or (b) the alternate base rate (greater of (i) the federal funds rate plus 0.5%, (ii) the prime rate, and (iii) third day LIBOR plus 1.00%) plus the applicable margin of 1.00% to 2.25%.
Superior Credit Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Consolidated EBITDA to interest expense ratio		2.50 to 1.00
Superior Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Funded debt to consolidated EBITDA ratio		4.00 to 1.00
Pledge agreement [Member] | Unit Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Collateral	we granted a security interest in the limited liability membership interests and other equity interests we own in Superior (which as of this report is 50% of the aggregate outstanding equity interests of Superior