Annual report pursuant to Section 13 and 15(d)

Note 19 - Supplemental Oil and Gas Disclosures - Change in Standard Measure of Discounted Future Net Cash Flows (Details)

v3.20.4
Note 19 - Supplemental Oil and Gas Disclosures - Change in Standard Measure of Discounted Future Net Cash Flows (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Changes in Standardized Measure      
Standardized measure, beginning of year $ 986.9 $ 1,067.0 $ 740.6
Sales and transfers of oil and gas produced, net of production costs (168.6) (315.8) (398.1)
Net changes in price, net of future production costs (503.7) (376.4) 571.5
Extensions and discoveries, net of future production and development costs 2.8 27.0 53.6
Changes in estimated future development costs (15.9) (6.0) (114.7)
Previously estimated development costs incurred 1.4 19.3 48.4
Revisions of quantity estimates (65.2) 116.4 307.6
Accretion of discount 111.8 107.4 50.5
Net change in income taxes (87.7) (62.9) 133.4
Purchases of reserves in-place 44.6 298.3 27.8
Sales of reserves in-place 0.0 0.0 (54.1)
Changes in production rates due to timing and other 11.9 (13.2) (32.7)
Net (decrease) increase (493.2) (80.1) 326.4
Standardized measure, end of year $ 493.7 $ 986.9 $ 1,067.0