XML 132 R144.htm IDEA: XBRL DOCUMENT v2.4.0.6
Supplemental Information on Oil and Natural Gas Producing Activities - Estimate of Changes in Standardized Measure of Discounted Future Net Cash Flows from Proved Reserves (Unaudited) (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Standardized Measure [Abstract]      
Present value, beginning balance $ 5,216,337 [1] $ 3,683,515 $ 1,560,978
Changes during the year      
Revenues less production and other costs (1,234,918) (857,848) (507,730)
Net changes in prices, production and other costs (2,555,391) 1,264,736 967,967
Development costs incurred 766,943 575,546 366,539
Net changes in future development costs (45,397) 87,080 (910,934)
Extensions and discoveries 2,092,423 1,812,167 955,540
Revisions of previous quantity estimates (530,755) (345,965) 773,132
Accretion of discount 678,200 455,501 159,971
Net change in income taxes 11,433 (833,841) (825,668)
Purchases of reserves in-place 1,708,301 44,934 1,133,413
Sales of reserves in-place (410,415) (558,257) (258)
Timing differences and other 143,607 [2] (111,231) [2] 10,565 [2]
Net change for the year 624,031 1,532,822 2,122,537
Present value, ending balance $ 5,840,368 [1] $ 5,216,337 [1] $ 3,683,515
[1] Includes approximately $952.7 million and $932.8 million attributable to noncontrolling interests at December 31, 2012 and 2011, respectively.
[2] The change in timing differences and other are related to revisions in the Company’s estimated time of production and development.