Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary Of Significant Accounting Policies [Line Items]
Percentage of non-operating working interest overriding royalty interests	15.00%
Interest costs capitalized	$ 11,800,000	$ 9,600,000	$ 5,300,000
Average DD&A Per Boe (in USD per BOE)	17.55	11.26	7.67
Capitalized interest	24,848,000	23,369,000	20,746,000
Reserves discount factor	10.00%
Deferred financing costs	23,900,000	20,300,000
Deferred financing costs, accumulated amortization	$ 3,500,000	$ 2,800,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life, minimum, years	5 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life, minimum, years	10 years
Stock Options And SARs [Member]
Summary Of Significant Accounting Policies [Line Items]
Vesting period, in years	3 years
Stock Options [Member]
Summary Of Significant Accounting Policies [Line Items]
Expiration period after date of grant, in years	10 years
Stock Appreciation Rights (SARs) [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expiration period after date of grant, in years	4 years
Stock Appreciation Rights (SARs) [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Expiration period after date of grant, in years	7 years
Restricted Stock Awards And Units [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Vesting period, in years	1 year
Restricted Stock Awards And Units [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Vesting period, in years	3 years
Restricted Stock Granted To Contractors [Member]
Summary Of Significant Accounting Policies [Line Items]
Vesting period, in years	3 years