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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Tables) | 12 Months Ended
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Dec. 31, 2019
Extractive Industries [Abstract] |
Schedule of capitalized costs related to oil and gas producing activities | Capitalized Costs Related to Oil and Gas Producing Activities
| 2019 |  | 2018
| (In thousands)
Proved properties | $ | 8,909,069 |  |  | $ | 7,153,799 |
Unproved properties | 1,686,666 |  |  | 2,873,037 |
| 10,595,735 |  |  | 10,026,836 |
Accumulated depreciation, depletion, amortization and impairment | (7,191,957 | ) |  | (4,613,293 | )
Net capitalized costs | $ | 3,403,778 |  |  | $ | 5,413,543 |
Equity investment in Grizzly Oil Sands ULC |  |  |
Proved properties | $ | 64,476 |  |  | $ | 67,475 |
Unproved properties | 85,395 |  |  | 79,605 |
| 149,871 |  |  | 147,080 |
Accumulated depreciation, depletion, amortization and impairment | (1,634 | ) |  | (1,553 | )
Net capitalized costs | $ | 148,237 |  |  | $ | 145,527 |
Schedule of cost incurred in oil and gas property acquisition and development activities | Costs Incurred in Oil and Gas Property Acquisition and Development Activities
| 2019 |  | 2018 |  | 2017
| (In thousands)
Acquisition | $ | 37,598 |  |  | $ | 119,444 |  |  | $ | 1,946,416 |
Development | 594,673 |  |  | 714,269 |  |  | 1,138,951 |
Exploratory | 9,762 |  |  | 22,081 |  |  | 9,058 |
Total | $ | 642,033 |  |  | $ | 855,794 |  |  | $ | 3,094,425 |
Equity investment in Grizzly Oil Sands ULC |  |  |  |  |
Acquisition | $ | — |  |  | $ | 238 |  |  | $ | 503 |
Development | — |  |  | — |  |  | — |
Exploratory | 849 |  |  | — |  |  | — |
Total | $ | 849 |  |  | $ | 238 |  |  | $ | 503 |
Schedule of results of operations for oil and gas production activities | The results of operations exclude general office overhead and interest expense attributable to oil and gas production.
| 2019 |  | 2018 |  | 2017
| (In thousands)
Revenues | $ | 1,137,648 |  |  | $ | 1,478,523 |  |  | $ | 1,106,624 |
Production costs | (403,294 | ) |  | (415,308 | ) |  | (350,367 | )
Depletion | (539,379 | ) |  | (476,517 | ) |  | (358,792 | )
Impairment | (2,039,770 | ) |  | — |  |  | — |
Income tax benefit | 7,563 |  |  | 68 |  |  | 240 |
Results of operations from producing activities | $ | (1,837,232 | ) |  | $ | 586,766 |  |  | $ | 397,705 |
Depletion per Mcf of gas equivalent (Mcfe) | $ | 1.08 |  |  | $ | 0.96 |  |  | $ | 0.90 |
Results of Operations from equity method investment in Grizzly Oil Sands ULC |  |  |  |  |
Revenues | $ | — |  |  | $ | — |  |  | $ | — |
Production costs | — |  |  | — |  |  | — |
Depletion | — |  |  | — |  |  | — |
Income tax expense | — |  |  | — |  |  | — |
Results of operations from producing activities | $ | — |  |  | $ | — |  |  | $ | — |
Schedule of oil and gas reserves | These estimates are reviewed annually and revised, either upward or downward, as warranted by additional performance data.
| 2019 |  | 2018 |  | 2017
| Oil |  | Natural Gas |  | NGL |  | Oil |  | Natural Gas |  | NGL |  | Oil |  | Natural Gas |  | NGL
| (Mbbls) |  | (MMcf) |  | (Mbbls) |  | (Mbbls) |  | (MMcf) |  | (Mbbls) |  | (Mbbls) |  | (MMcf) |  | (Mbbls)
Proved Reserves |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning of the period | 21,050 |  |  | 4,133,889 |  |  | 80,520 |  |  | 19,157 |  |  | 4,825,310 |  |  | 75,766 |  |  | 5,546 |  |  | 2,167,068 |  |  | 20,127 |
Purchases in oil and natural gas reserves in place | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | 15,132 |  |  | 1,098,644 |  |  | 53,617 |
Extensions and discoveries | 3,612 |  |  | 997,014 |  |  | 12,992 |  |  | 5,205 |  |  | 622,271 |  |  | 9,631 |  |  | 951 |  |  | 1,594,734 |  |  | 4,619 |
Sales of oil and natural gas reserves in place | (2,369 | ) |  | (62,557 | ) |  | — |  |  | (134 | ) |  | (43,444 | ) |  | (112 | ) |  | — |  |  | — |  |  | — |
Revisions of prior reserve estimates | (1,749 | ) |  | (561,890 | ) |  | (26,909 | ) |  | (377 | ) |  | (826,506 | ) |  | 1,228 |  |  | 107 |  |  | 314,925 |  |  | 2,737 |
Current production | (2,186 | ) |  | (458,178 | ) |  | (5,074 | ) |  | (2,801 | ) |  | (443,742 | ) |  | (5,993 | ) |  | (2,579 | ) |  | (350,061 | ) |  | (5,334 | )
End of period | 18,357 |  |  | 4,048,279 |  |  | 61,528 |  |  | 21,050 |  |  | 4,133,889 |  |  | 80,520 |  |  | 19,157 |  |  | 4,825,310 |  |  | 75,766 |
Proved developed reserves | 7,887 |  |  | 1,757,303 |  |  | 29,898 |  |  | 9,570 |  |  | 1,813,184 |  |  | 40,810 |  |  | 10,245 |  |  | 1,616,930 |  |  | 36,247 |
Proved undeveloped reserves | 10,470 |  |  | 2,290,976 |  |  | 31,630 |  |  | 11,480 |  |  | 2,320,705 |  |  | 39,710 |  |  | 8,912 |  |  | 3,208,380 |  |  | 39,519 |
Equity investment in Grizzly Oil Sands ULC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Beginning of the period | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Purchases in oil and natural gas reserves in place | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Extensions and discoveries | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Revisions of prior reserve estimates | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Current production | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
End of period | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Proved developed reserves | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Proved undeveloped reserves | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |  |  | — |
Schedule of standardized measure of discounted future net cash flows relating to proved oil and gas reserves | Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves
| Year ended December 31,
| 2019 |  | 2018 |  | 2017
| (In thousands)
Future cash flows | $ | 10,451,179 |  |  | $ | 14,483,197 |  |  | $ | 11,202,692 |
Future development and abandonment costs | (2,058,374 | ) |  | (2,437,853 | ) |  | (3,005,217 | )
Future production costs | (4,512,940 | ) |  | (5,067,554 | ) |  | (2,152,821 | )
Future production taxes | (332,525 | ) |  | (455,840 | ) |  | (289,944 | )
Future income taxes | — |  |  | (943,293 | ) |  | (573,965 | )
Future net cash flows | 3,547,340 |  |  | 5,578,657 |  |  | 5,180,745 |
10% discount to reflect timing of cash flows | (1,843,753 | ) |  | (2,595,932 | ) |  | (2,537,181 | )
Standardized measure of discounted future net cash flows | $ | 1,703,587 |  |  | $ | 2,982,725 |  |  | $ | 2,643,564 |
Equity investment in Grizzly Oil Sands ULC Standardized measure of discounted cash flows |  |  |  |  |
Future cash flows | $ | — |  |  | $ | — |  |  | $ | — |
Future development and abandonment costs | — |  |  | — |  |  | — |
Future production costs | — |  |  | — |  |  | — |
Future production taxes | — |  |  | — |  |  | — |
Future income taxes | — |  |  | — |  |  | — |
Future net cash flows | — |  |  | — |  |  | — |
10% discount to reflect timing of cash flows |  |  |  |  |  |  |  |
Standardized measure of discounted future net cash flows | $ | — |  |  | $ | — |  |  | $ | — |
Schedule of changes in standardized measure of discounted future net cash flows relating to proved oil and gas reserves | Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves
| Year ended December 31,
| 2019 |  | 2018 |  | 2017
| (In thousands)
Sales and transfers of oil and gas produced, net of production costs | $ | (734,354 | ) |  | $ | (1,063,215 | ) |  | $ | (756,257 | )
Net changes in prices, production costs, and development costs | (1,372,443 | ) |  | 590,519 |  |  | 913,714 |
Acquisition of oil and gas reserves in place | — |  |  | — |  |  | 703,866 |
Extensions and discoveries | 388,151 |  |  | 519,137 |  |  | 618,039 |
Previously estimated development costs incurred during the period | 405,979 |  |  | 402,156 |  |  | 390,673 |
Revisions of previous quantity estimates, less related production costs | (321,397 | ) |  | (356,933 | ) |  | 155,200 |
Sales of oil and gas reserves in place | (48,547 | ) |  | (25,882 | ) |  | — |
Accretion of discount | 298,273 |  |  | 264,356 |  |  | 68,804 |
Net changes in income taxes | 424,628 |  |  | (185,157 | ) |  | (231,545 | )
Change in production rates and other | (319,428 | ) |  | 194,180 |  |  | 93,030 |
Total change in standardized measure of discounted future net cash flows | $ | (1,279,138 | ) |  | $ | 339,161 |  |  | $ | 1,955,524 |
Equity investment in Grizzly Oil Sands ULC Changes in standardized measure of discounted cash flows |  |  |  |  |
Sales and transfers of oil and gas produced, net of production costs | $ | — |  |  | $ | — |  |  | $ | — |
Net changes in prices, production costs, and development costs | — |  |  | — |  |  | — |
Acquisition of oil and gas reserves in place | — |  |  | — |  |  | — |
Extensions and discoveries | — |  |  | — |  |  | — |
Previously estimated development costs incurred during the period | — |  |  | — |  |  | — |
Revisions of previous quantity estimates, less related production costs | — |  |  | — |  |  | — |
Accretion of discount | — |  |  | — |  |  | — |
Net changes in income taxes | — |  |  | — |  |  | — |
Change in production rates and other | — |  |  | — |  |  | — |
Total change in standardized measure of discounted future net cash flows | $ | — |  |  | $ | — |  |  | $ | — |

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