Acquisitions and Divestitures (Tables)

12 Months Ended

Dec. 31, 2012

Acquisitions and divestitures [Abstract]

Schedule of Purchase Price Allocation

The Noble acquisition is accounted for using the acquisition method under ASC 805, Business Combinations, which requires that the acquired assets and liabilities be recorded at their fair values as of the acquisition date. The following table summarizes the adjusted purchase price and the estimated values of assets acquired and liabilities assumed. It is based on information available to us at the time these consolidated financial statements were prepared. We believe these estimates are reasonable; however, the estimates are subject to change as additional information becomes available and is assessed by us (in thousands):

Adjusted Purchase Price
Total consideration given	$	592,627
Adjusted Allocation of Purchase Price
Oil and natural gas properties included in the full cost pool:
Proved oil and natural gas properties	$	260,799
Undeveloped oil and natural gas properties	353,343
Total oil and natural gas properties included in the full cost pool (1)	614,142
Gas gathering and processing equipment and other	25,163
Asset retirement obligation	(46,678		)
Fair value of net assets acquired	$	592,627

(1) We used a discounted cash flow model and made market assumptions as to future commodity prices, projections of estimated quantities of oil and natural gas reserves, expectations for timing and amount of future development and operating costs, projections of future rates of production, expected recovery rates and risk adjusted discount rates.

Pro Forma Results

The following unaudited pro forma financial information is presented to reflect the operations of the acquired assets as if the acquisition had been completed on January 1, 2011. The unaudited pro forma financial information was derived from the historical accounting records of the seller adjusted for estimated transaction costs, depreciation, depletion and amortization, ceiling test impact, general and administrative expenses, capitalized interest, and interest on the $400.0 million of bonds issued along with additional borrowings under our credit agreement to finance the acquisition. The unaudited pro forma financial information does not purport to be indicative of results of operations that would have occurred had the transaction occurred on the basis assumed above, nor is such information indicative of our expected future results of operations. The pro forma results of operations do not include any cost savings or other synergies that resulted, or may result, from the acquisition or any estimated costs that will be incurred to integrate these assets. Future results may vary significantly from the results reflected in this pro forma financial information because of future events and transactions, as well as other factors.

	Twelve months ended December 31,
	2012		2011
	(In thousands, except per share amounts)
Pro forma:
Revenues	$	1,376,393	$	1,336,227
Net income	$	83,940	$	229,272
Net income per common share:
Basic	$	1.75	$	4.81
Diluted	$	1.74	$	4.78