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SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION - Supplemental Schedule Of Cash Flow Information (Details) $ in Millions, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 CAD ($) | Dec. 31, 2016 CAD ($) | Dec. 31, 2015 CAD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2017 CAD ($)
Disclosure Of Detailed Information About Cash Flows [Line Items] |  |  |  |  |  |
Accounts receivable |  | $ (977) | $ (142) | $ 615 |  |
Current income tax assets |  | 527 | (165) | (447) |  |
Inventory |  | 81 | (79) | 142 |  |
Prepaids and other |  | (28) | 14 | 11 |  |
Accounts payable |  | 175 | 31 | 7 |  |
Accrued liabilities |  | 365 | (116) | (981) |  |
Other long-term liabilities |  | 469 | 0 | 0 |  |
Net changes in non-cash working capital |  | 612 | (457) | (653) |  |
Net change in non-cash working capital |  | 299 | (542) | 239 |  |
Net change in non-cash working capital |  | 0 | 0 | (40) |  |
Net change in non-cash working capital, investing activities |  | 313 | 85 | (852) |  |
Exploration and evaluation assets |  |  |  |  |  |
Expenditures on exploration and evaluation assets |  | 159 | 29 | 180 |  |
Net proceeds on sale of exploration and evaluation assets |  | (35) | (35) | (416) |  |
Net expenditures (proceeds) on exploration and evaluation assets | [1] | 124 | (6) | (236) |  |
Property, plant and equipment |  |  |  |  |  |
Expenditures on property, plant and equipment |  | 4,574 | 4,152 | 5,118 |  |
Net proceeds on sale of property, plant and equipment |  | 0 | (349) | (414) |  |
Net expenditures on property, plant and equipment | [1],[2] | $ 4,574 | 3,803 | 4,704 |  |
Investment in PrairieSky Royalty Ltd. |  |  |  |  |  |
Property, plant and equipment |  |  |  |  |  |
Non-cash share consideration received |  |  |  | $ 985 |  |
Disposal of Cold Lake Pipeline | Investment in Inter Pipeline Ltd. |  |  |  |  |  |
Property, plant and equipment |  |  |  |  |  |
Non-cash share consideration received |  |  | $ 190 |  |  |
AOSP |  |  |  |  |  |
Property, plant and equipment |  |  |  |  |  |
Deferred purchase consideration payable |  |  |  |  | $ 375 | $ 469
[1] | Net proceeds on exploration and evaluation assets and net expenditures on property, plant and equipment in 2015 exclude non-cash share consideration of $985 million received from PrairieSky Royalty Ltd. ("PrairieSky") on the disposition of royalty income assets.
[2] | Net expenditures on property, plant and equipment in 2016 exclude non-cash share consideration of $190 million received from Inter Pipeline Ltd. ("Inter Pipeline") on the disposition of the Company's interest in the Cold Lake Pipeline.

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