Acquisitions and Divestitures (Tables)

12 Months Ended

Dec. 31, 2011

Business Combinations [Abstract]

Consideration paid to sellers and recognized amounts of identifiable assets acquired and liabilities assumed

	(in thousands)
Consideration paid to sellers:
Cash consideration	$	128,398
Recognized amounts of identifiable assets acquired and liabilities assumed:
Proved developed and undeveloped properties	128,697
Asset retirement obligation	(119		)
Other liabilities assumed	(180		)
Total identifiable net assets	$	128,398

	(in thousands)
Consideration paid to sellers:
Cash consideration	$	327,032
Recognized amounts of identifiable assets acquired and liabilities assumed:
Proved developed and undeveloped properties	332,214
Other assets acquired	342
Asset retirement obligation	(3,498		)
Deferred income tax liability	(647		)
Other liabilities assumed	(333		)
Total identifiable net assets	$	328,078

Schedule of Earnings from discontinued operations, net of tax on the accompanying Statement of Operations

	Year Ended December 31, 2009
Sales of oil and natural gas(1)	$	11,555
Loss on sale of asset	(908		)
Other revenue	623
Total revenues	11,270
Realized and unrealized (gain) on derivatives, net	(13,786		)
Other expenses(2)	15,799
Total expenses	2,013
Earnings from discontinued operations, before income taxes	9,257
Provision for income taxes	2,451
Net earnings from discontinued operations	$	6,806

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