Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2009	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Line Items]
Number of daywork contracts		62
Book overdrafts		$ 26,500,000	$ 13,100,000
Concentration of cash		31,100,000	23,800,000
Minimum depreciation percentage for drilling rigs		20.00%
Goodwill impairment		0	0	0
Additions to goodwill		0	0	0
Goodwill deductible for tax purposes		5,700,000
Intangible asset impairment		0	0	0
Amortization		1,200,000	2,600,000	3,700,000
Accumulated amortization		16,100,000	14,900,000
Amortization to be recorded in 2012		1,200,000
Amortization to be recorded in 2013		700,000
Directly related overhead costs capitalized		15,600,000	13,400,000	13,200,000
Average rates used for depreciation, depletion and amortization per Boe		15.06	11.94	11.22
Undeveloped leasehold properties excluded from DD&A calculation		185,632,000
Future discounted net cash flows discounted		10.00%
Non-cash ceiling test write-down	281,200,000
Non-cash ceiling test write-down net of tax	175,100,000
Effects of cash flow hedges	197,900,000	22,100,000
Elimination of inter-segment revenue		52,221,000	40,143,000	15,049,000
Eliminated associated operating expense		32,600,000	31,000,000	13,700,000
Eliminated yielding		19,600,000	9,100,000	1,300,000
Number of partnerships		16
More-likely-than-not threshold		50.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days for drilling of one well		20
Duration length of contracts		6
Insurance coverage		50,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of days for drilling of one well		90
Duration length of contracts		3
Insurance coverage		1,500,000
Under-Produced Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Natural gas balancing		3,400,000,000
Over-Produced Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Natural gas balancing		3,300,000,000
Natural Gas Balancing [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable		1,500,000
Liability recognized to under production		$ 3,300,000
Jan'12 - Dec'12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, Bcfe/MMBoe		5.0
Jan'13 - Dec'13 [Member]
Summary Of Significant Accounting Policies [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, Bcfe/MMBoe		0.7
Jan'09 - Dec'09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, Bcfe/MMBoe	30.3
Jan'10 - Dec'10 [Member]
Summary Of Significant Accounting Policies [Line Items]
Oil and gas production volume covered by hedges that affect ceiling determination, Bcfe/MMBoe	33.2
Drilling Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives maximum, years		15
Property, Plant and Equipment, Other Types [Member]
Summary Of Significant Accounting Policies [Line Items]
Useful lives minimum, years		3
Useful lives maximum, years		15