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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) - Oil and Gas Reserves (Details) bbl in Thousands, Mcf in Thousands | 12 Months Ended
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Dec. 31, 2016 Mcf bbl | Dec. 31, 2015 Mcf bbl | Dec. 31, 2014 Mcf bbl
Oil derivatives |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | 6,458 | 9,497 | 8,346
Purchases in oil and gas reserves in place | 0 | 0 | 173
Extensions and discoveries | 1,217 | 2,413 | 4,975
Revisions of prior reserve estimates | (3) | (2,553) | (1,313)
Current production | (2,126) | (2,899) | (2,684)
End of period | 5,546 | 6,458 | 9,497
Proved developed reserves | 4,882 | 6,120 | 5,719
Proved undeveloped reserves | 664 | 338 | 3,778
Natural gas liquids derivatives |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | Mcf | 1,560,145 | 719,006 | 146,446
Purchases in oil and gas reserves in place | Mcf | 0 | 371,663 | 8,863
Extensions and discoveries | Mcf | 1,082,220 | 997,057 | 629,151
Revisions of prior reserve estimates | Mcf | (247,703) | (371,430) | (6,136)
Current production | Mcf | (227,594) | (156,151) | (59,318)
End of period | Mcf | 2,167,068 | 1,560,145 | 719,006
Proved developed reserves | Mcf | 744,797 | 652,961 | 345,166
Proved undeveloped reserves | Mcf | 1,422,271 | 907,184 | 373,840
Natural gas liquids |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | 17,736 | 26,268 | 5,675
Purchases in oil and gas reserves in place | 0 | 0 | 353
Extensions and discoveries | 7,677 | 5,486 | 22,594
Revisions of prior reserve estimates | (1,439) | (9,594) | (304)
Current production | (3,847) | (4,424) | (2,050)
End of period | 20,127 | 17,736 | 26,268
Proved developed reserves | 14,299 | 12,910 | 12,379
Proved undeveloped reserves | 5,828 | 4,826 | 13,889
Investment in Grizzly Oil Sands ULC | Oil derivatives |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | 0 | 14,558 | 13,637
Purchases in oil and gas reserves in place | 0 | 0 | 0
Extensions and discoveries | 0 | 0 | 0
Revisions of prior reserve estimates | 0 | (14,530) | 990
Current production | 0 | (28) | (69)
End of period | 0 | 0 | 14,558
Proved developed reserves | 0 | 0 | 1,632
Proved undeveloped reserves | 0 | 0 | 12,926
Investment in Grizzly Oil Sands ULC | Natural gas liquids derivatives |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | Mcf | 0 | 0 | 0
Purchases in oil and gas reserves in place | Mcf | 0 | 0 | 0
Extensions and discoveries | Mcf | 0 | 0 | 0
Revisions of prior reserve estimates | Mcf | 0 | 0 | 0
Current production | Mcf | 0 | 0 | 0
End of period | Mcf | 0 | 0 | 0
Proved developed reserves | Mcf | 0 | 0 | 0
Proved undeveloped reserves | Mcf | 0 | 0 | 0
Investment in Grizzly Oil Sands ULC | Natural gas liquids |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |
Beginning of the period | 0 | 0 | 0
Purchases in oil and gas reserves in place | 0 | 0 | 0
Extensions and discoveries | 0 | 0 | 0
Revisions of prior reserve estimates | 0 | 0 | 0
Current production | 0 | 0 | 0
End of period | 0 | 0 | 0
Proved developed reserves | 0 | 0 | 0
Proved undeveloped reserves | 0 | 0 | 0

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- Definition Proved Developed and Undeveloped Reserves [Roll Forward] + References No definition available. + Details
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- Definition Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-10.(a)(2)) -URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e511914-122862 + Details
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- Definition Production of proved reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Purchase of minerals in place. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Revisions represent changes in previous estimates of proved reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61831-109447 + Details
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- Definition Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61884-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61797-109447 + Details
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- Definition Net quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other renewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61884-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68064819&loc=d3e61797-109447 + Details
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