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Supplemental Oil and Gas Information (Summary of Proved Reserves Based on Average Prices) (Details) MMBbls in Millions, ft³ in Billions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 MMcf ft³ MMBbls | Dec. 31, 2017 ft³ MMBbls | Dec. 31, 2017 ft³ MMBbls | Dec. 31, 2016 ft³ MMBbls | Dec. 31, 2015 ft³ MMBbls | Dec. 31, 2014 ft³ MMBbls
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 329.0 | 456.2 | 441.8 |
Revisions of previous estimates |  |  |  | (6.0) | (5.8) | 5.3 |
Improved recovery |  |  |  | 2.0 |  | 2.4 |
Extensions and discoveries |  |  |  | 31.6 | 11.0 | 63.8 |
Purchases of properties |  |  |  | 4.7 | 26.3 |  |
Sales of properties |  |  |  |  | (121.0) | (11.0) |
Production |  |  |  | (33.2) | (37.7) | (46.1) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 328.1 | 329.0 | 456.2 |
Proved developed reserves |  | 185.5 | 185.5 | 185.5 | 184.9 | 326.6 | 324.1
Proved undeveloped reserves |  | 142.6 | 142.6 | 142.6 | 144.1 | 129.6 | 117.7
Crude Oil [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 329.0 | 341.4 | 336.2 |
Revisions of previous estimates |  |  |  | (6.0) | (5.8) | (8.2) |
Improved recovery |  |  |  | 2.0 |  | 2.4 |
Extensions and discoveries |  |  |  | 31.6 | 11.0 | 63.8 |
Purchases of properties |  |  |  | 4.7 | 26.3 |  |
Sales of properties |  |  |  |  | (7.8) | (11.0) |
Production |  |  |  | (33.2) | (36.1) | (41.8) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 328.1 | 329.0 | 341.4 |
Proved developed reserves |  | 185.5 | 185.5 | 185.5 | 184.9 | 211.8 | 218.5
Proved undeveloped reserves |  | 142.6 | 142.6 | 142.6 | 144.1 | 129.6 | 117.7
Natural Gas Liquids Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 42.5 | 36.4 | 30.6 |
Revisions of previous estimates |  |  |  | 1.3 | 1.6 | 2.0 |
Extensions and discoveries |  |  |  | 7.8 | 2.9 | 7.6 |
Purchases of properties |  |  |  | 0.5 | 5.1 |  |
Sales of properties |  |  |  |  |  | (0.1) |
Production |  |  |  | (3.2) | (3.5) | (3.7) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 48.9 | 42.5 | 36.4 |
Proved developed reserves |  | 24.6 | 24.6 | 24.6 | 22.2 | 21.6 | 17.5
Proved undeveloped reserves |  | 24.3 | 24.3 | 24.3 | 20.3 | 14.8 | 13.1
Natural Gas Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance | ft³ |  |  | 1,878.0 |  | 1,688.8 | 1,704.7 |
Revisions of previous estimates | ft³ |  |  | (5.4) |  | 43.3 | 53.5 |
Improved recovery | ft³ |  |  |  |  |  | 1.8 |
Extensions and discoveries | ft³ |  |  | 190.6 |  | 164.2 | 162.9 |
Purchases of properties | ft³ |  |  | 4.0 |  | 122.3 |  |
Sales of properties | ft³ |  |  |  |  | (2.2) | (78.0) |
Production | ft³ |  |  | (140.1) |  | (138.4) | (156.1) |
Proved developed and undeveloped reserves, Ending Balance | ft³ |  |  | 1,927.1 |  | 1,878.0 | 1,688.8 |
Proved developed reserves | ft³ |  | 819.3 | 819.3 | 819.3 | 818.1 | 783.5 | 812.1
Proved undeveloped reserves | ft³ |  | 1,107.8 | 1,107.8 | 1,107.8 | 1,059.9 | 905.3 | 892.6
United States [Member] | Crude Oil [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 214.4 | 238.9 | 204.9 |
Revisions of previous estimates |  |  |  | (4.7) | (10.9) | (7.6) |
Extensions and discoveries |  |  |  | 27.2 | 8.6 | 63.8 |
Purchases of properties |  |  |  | 4.7 |  |  |
Sales of properties |  |  |  |  | (4.5) |  |
Production |  |  |  | (16.9) | (17.7) | (22.2) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 224.7 | 214.4 | 238.9 |
Proved developed reserves |  | 126.3 | 126.3 | 126.3 | 113.9 | 125.9 | 106.2
Proved undeveloped reserves |  | 98.4 | 98.4 | 98.4 | 100.5 | 113.0 | 98.7
United States [Member] | Natural Gas Liquids Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 36.4 | 35.4 | 29.1 |
Revisions of previous estimates |  |  |  | 2.0 | 1.2 | 2.2 |
Extensions and discoveries |  |  |  | 7.0 | 2.8 | 7.6 |
Purchases of properties |  |  |  | 0.5 |  |  |
Production |  |  |  | (2.9) | (3.0) | (3.5) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 43.0 | 36.4 | 35.4 |
Proved developed reserves |  | 23.3 | 23.3 | 23.3 | 20.8 | 20.7 | 16.5
Proved undeveloped reserves |  | 19.7 | 19.7 | 19.7 | 15.6 | 14.7 | 12.6
United States [Member] | Natural Gas Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance | ft³ |  |  | 219.4 |  | 232.4 | 226.3 |
Revisions of previous estimates | ft³ |  |  | (16.0) |  | 0.1 | (5.2) |
Extensions and discoveries | ft³ |  |  | 32.2 |  | 6.4 | 43.2 |
Purchases of properties | ft³ |  |  | 4.0 |  |  |  |
Sales of properties | ft³ |  |  |  |  | (0.1) |  |
Production | ft³ |  |  | (16.3) |  | (19.4) | (31.9) |
Proved developed and undeveloped reserves, Ending Balance | ft³ |  |  | 223.3 |  | 219.4 | 232.4 |
Proved developed reserves | ft³ |  | 127.7 | 127.7 | 127.7 | 138.7 | 148.3 | 145.6
Proved undeveloped reserves | ft³ |  | 95.6 | 95.6 | 95.6 | 80.7 | 84.1 | 80.7
Canada [Member] | Crude Oil [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 48.9 | 27.9 | 37.4 |
Revisions of previous estimates |  |  |  | 2.3 | 2.5 | (4.8) |
Extensions and discoveries |  |  |  | 4.4 |  |  |
Purchases of properties |  |  |  |  | 26.3 |  |
Sales of properties |  |  |  |  | (3.3) |  |
Production |  |  |  | (4.1) | (4.5) | (4.7) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 51.5 | 48.9 | 27.9 |
Proved developed reserves |  | 21.9 | 21.9 | 21.9 | 19.2 | 23.8 | 32.4
Proved undeveloped reserves |  | 29.6 | 29.6 | 29.6 | 29.7 | 4.1 | 5.0
Canada [Member] | Synthetic Oil [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance | [1] |  |  | 0.0 | 114.8 | 105.6 |
Revisions of previous estimates | [1] |  |  |  |  | 13.5 |
Sales of properties | [1] |  |  |  | (113.2) |  |
Production | [1] |  |  |  | (1.6) | (4.3) |
Proved developed and undeveloped reserves, Ending Balance | [1] |  |  |  | 0.0 | 114.8 |
Proved developed reserves | [1] |  |  |  |  | 114.8 | 105.6
Canada [Member] | Natural Gas Liquids Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 5.6 | 0.4 | 0.7 |
Revisions of previous estimates |  |  |  | (0.6) | 0.2 | (0.3) |
Extensions and discoveries |  |  |  | 0.8 | 0.1 |  |
Purchases of properties |  |  |  |  | 5.1 |  |
Production |  |  |  | (0.2) | (0.2) |  |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 5.6 | 5.6 | 0.4 |
Proved developed reserves |  | 1.0 | 1.0 | 1.0 | 0.9 | 0.3 | 0.2
Proved undeveloped reserves |  | 4.6 | 4.6 | 4.6 | 4.7 | 0.1 | 0.5
Canada [Member] | Natural Gas Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance | ft³ |  |  | 1,118.9 |  | 909.6 | 842.8 |
Revisions of previous estimates | ft³ |  |  | 19.4 |  | 45.3 | 18.9 |
Extensions and discoveries | ft³ |  |  | 156.7 |  | 120.2 | 119.7 |
Purchases of properties | ft³ |  |  |  |  | 122.3 |  |
Sales of properties | ft³ |  |  |  |  | (2.1) |  |
Production | ft³ |  |  | (82.6) |  | (76.4) | (71.8) |
Proved developed and undeveloped reserves, Ending Balance | ft³ |  |  | 1,212.4 |  | 1,118.9 | 909.6 |
Proved developed reserves | ft³ |  | 547.0 | 547.0 | 547.0 | 498.9 | 453.5 | 467.4
Proved undeveloped reserves | ft³ |  | 665.5 | 665.5 | 665.5 | 620.0 | 456.1 | 375.4
Malaysia [Member] | Crude Oil [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 65.7 | 74.6 | 93.9 |
Revisions of previous estimates |  |  |  | (3.6) | 2.6 | 4.2 |
Improved recovery |  |  |  | 2.0 |  | 2.4 |
Extensions and discoveries |  |  |  |  | 2.4 |  |
Sales of properties |  |  |  |  |  | (11.0) |
Production |  |  |  | (12.2) | (13.9) | (14.9) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 51.9 | 65.7 | 74.6 |
Proved developed reserves |  | 37.3 | 37.3 | 37.3 | 51.8 | 62.1 | 79.9
Proved undeveloped reserves |  | 14.6 | 14.6 | 14.6 | 13.9 | 12.5 | 14.0
Malaysia [Member] | Oil Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 52.2 |  |  |
Malaysia [Member] | Natural Gas Liquids Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance |  |  |  | 0.5 | 0.6 | 0.8 |
Revisions of previous estimates |  |  |  | (0.1) | 0.2 | 0.1 |
Sales of properties |  |  |  |  |  | (0.1) |
Production |  |  |  | (0.1) | (0.3) | (0.2) |
Proved developed and undeveloped reserves, Ending Balance |  |  |  | 0.3 | 0.5 | 0.6 |
Proved developed reserves |  | 0.3 | 0.3 | 0.3 | 0.5 | 0.6 | 0.8
Malaysia [Member] | Natural Gas Reserves [Member] |  |  |  |  |  |  |
Proved developed and undeveloped oil reserves: |  |  |  |  |  |  |
Proved developed and undeveloped crude oil/synthetic oil reserves, Beginning Balance | ft³ |  |  | 539.7 |  | 546.8 | 635.6 |
Revisions of previous estimates | ft³ |  |  | (8.8) |  | (2.1) | 39.8 |
Improved recovery | ft³ |  |  |  |  |  | 1.8 |
Extensions and discoveries | ft³ |  |  | 1.7 |  | 37.6 |  |
Sales of properties | ft³ |  |  |  |  |  | (78.0) |
Production | ft³ |  |  | (41.2) |  | (42.6) | (52.4) |
Proved developed and undeveloped reserves, Ending Balance |  | 491,300 | 491.4 |  | 539.7 | 546.8 |
Proved developed reserves | ft³ |  | 144.6 | 144.6 | 144.6 | 180.5 | 181.7 | 199.1
Proved undeveloped reserves | ft³ |  | 346.7 | 346.7 | 346.7 | 359.2 | 365.1 | 436.5
[1] | All synthetic oil operations were sold in June 2016.

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