Summary Of Significant Accounting Policies (Narrative) (Details)		12 Months Ended
		Dec. 31, 2017 USD ($) contract Unit rig MMcf	Dec. 31, 2016 USD ($) rig		Dec. 31, 2015 USD ($) rig systems
Summary Of Significant Accounting Policies [Line Items]
Number of daywork contracts | contract		9
Number of contracts, daywork expiring in one year | contract		8
Number of contracts, daywork expiring in two years | contract		1
Book Overdrafts		$ 12,400,000	$ 17,300,000
Concentration of cash		11,400,000	8,300,000
Interest Costs Capitalized		15,900,000	15,300,000		$ 21,700,000
Goodwill impairment		0	0		0
Additions to goodwill		$ 0	0		0
Percentage fair value exceeds carrying value for goodwill		41.00%
Goodwill deductible for tax purposes		$ 700,000
Directly related overhead costs capitalized		14,800,000	15,400,000		19,200,000
Average rates used for depreciation, depletion, and amortization per Boe		6.00	6.24		12.30
Unproved properties not being amortized		$ 296,764,000	314,867,000		337,099,000
Future discounted net cash flows discounted		10.00%
Unproved properties included in amortization		$ 10,500,000	7,600,000		114,400,000
Revenues from transactions with operating segments of same entity		13,400,000	0		22,100,000
Eliminated associated operating expense		11,800,000	0		18,300,000
Eliminated yielding		$ 1,600,000	$ 0		3,800,000
Number of oil and gas limited partnerships | Unit		13
Federal statutory income tax rate, percent			35.00%
Tax benefit from change in enacted tax rate	[1]	$ (81,307,000)	$ 0		$ 0
Liability recognized to under production		$ (3,283,000)	$ (3,789,000)
Minimum
Summary Of Significant Accounting Policies [Line Items]
Number of days for drilling of one well		10 days
Duration length of contracts		6 months
Insurance coverage		$ 0
Maximum
Summary Of Significant Accounting Policies [Line Items]
Number of days for drilling of one well		90 days
Duration length of contracts		2 years
Insurance coverage		$ 1,000,000
Under-Produced Properties
Summary Of Significant Accounting Policies [Line Items]
Natural gas balancing (MMcf) | MMcf		3,700
Over-Produced Properties
Summary Of Significant Accounting Policies [Line Items]
Natural gas balancing (MMcf) | MMcf		3,800
Natural Gas Balancing
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable		$ 2,400,000
Drilling Equipment
Summary Of Significant Accounting Policies [Line Items]
Minimum depreciation percentage for idle drilling rigs		20.00%
Number of rigs sold | rig		0	1		31
Impairment of contract drilling equipment		$ 0	$ 0		$ 8,300,000
Net book value of drilling rigs sold			1,700,000.0		11,300,000
Gain (loss) on sale of drilling rigs			1,600,000		(7,300,000)
Drilling Equipment | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life, years		15 years
Building
Summary Of Significant Accounting Policies [Line Items]
Useful life, years		39 years
Property, Plant and Equipment, Other Types | Minimum
Summary Of Significant Accounting Policies [Line Items]
Useful life, years		3 years
Property, Plant and Equipment, Other Types | Maximum
Summary Of Significant Accounting Policies [Line Items]
Useful life, years		15 years
Gas Gathering and Processing Equipment
Summary Of Significant Accounting Policies [Line Items]
Impairment of gas gathering systems		$ 0	0		$ 27,000,000
Number of gas gathering systems impaired | systems					3
Oil and Natural Gas
Summary Of Significant Accounting Policies [Line Items]
Impairment of oil and natural gas properties		0	161,563,000		$ 1,599,348,000
Non-cash ceiling test write-down net of tax		$ 0	100,600,000		1,000,000,000
Oil and Natural Gas
Summary Of Significant Accounting Policies [Line Items]
Impairment of oil and natural gas properties			161,563,000	[2]	$ 1,599,348,000	[3]
Non-cash ceiling test write-down net of tax			$ 100,600,000
Effective starting 2018 [Member]
Summary Of Significant Accounting Policies [Line Items]
Federal statutory income tax rate, percent		21.00%

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

[2] We incurred non-cash ceiling test write-down of our oil and natural gas properties of $161.6 million pre-tax ($100.6 million, net of tax).

[3] We incurred non-cash ceiling test write-down of our oil and natural gas properties of $1.6 billion pre-tax ($1.0 billion, net of tax). Impairment for contract drilling equipment includes an $8.3 million pre-tax write-down for 30 drilling rigs and other drilling equipment. Impairment for gas gathering and processing systems includes $27.0 million pre-tax write-down for three of our systems, Bruceton Mills, Midwell, and Spring Creek.