Acquisitions and Divestitures (Tables)

12 Months Ended

Dec. 31, 2012

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