Annual report pursuant to Section 13 and 15(d)

Supplemental Oil and Gas Disclosures - Schedule of Changes in Standardized Measure (Details)

v3.3.1.900
Supplemental Oil and Gas Disclosures - Schedule of Changes in Standardized Measure (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Changes in Standardized Measure      
Changes in Standardized Measure, beginning of year $ 1,702.8 $ 1,674.6 $ 1,846.4
Sales and transfers of oil and gas produced, net of production costs (289.1) (650.9) (686.1)
Net changes in price, net of future production costs (1,455.6) (278.6) (65.2)
Extensions and discoveries, net of future production and development costs 65.3 309.6 393.8
Changes in estimated future development costs (8.5) (56.4) (91.1)
Previously estimated development costs incurred 158.9 263.1 262.1
Revisions of quantity estimates 137.9 118.6 (91.6)
Accretion of discount 150.6 180.6 202.2
Net change in income taxes 600.8 (11.4) 56.6
Purchases of reserves in-place 6.0 86.7 79.6
Sales of reserves in-place (401.4)   (53.1)
Changes in production rates due to timing and other (53.8) 66.9 (179.0)
Net increase (decrease) in standardized measure (1,088.9) 28.2 (171.8)
Changes in Standardized measure, end of year $ 613.9 $ 1,702.8 $ 1,674.6