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Other long-term liabilities and deferred credits - Schedule of Long-Term Liabilities and Deferred Credits (Detail) - CAD | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Other Long-term Liabilities |  |  |
Advances in aid of construction (a) | CAD 78,636,000 | CAD 105,191,000 |
Environmental remediation obligation (b) | 68,147,000 | 63,378,000 | CAD 71,529,000
Asset retirement obligations (c) | 55,406,000 | 24,822,000 |
Customer deposits (d) | 35,790,000 | 14,881,000 |
Unamortized investment tax credits (e) | 22,379,000 | 0 |
Deferred credits (f) | 26,555,000 | 44,544,000 |
Other | 55,779,000 | 22,790,000 |
Other Liabilities | 342,692,000 | 275,606,000 |
Less current portion | (57,586,000) | (43,157,000) |
Other long-term liabilities | 285,106,000 | 232,449,000 |
Transfers from advances in aid of construction to contributions in aid of construction | 13,626,000 | 23,986,000 |
Estimated environmental remediation costs | 71,873,000 | 76,853,000 |
Accrual for environmental loss contingencies to be incurred over next three years | CAD 25,186,000 |  |
Accrual for environmental loss contingencies, payment period | 28 years |  |
Amount of regulatory assets | CAD 551,134,000 | 291,964,000 |
Obligation incurred | 2,604,000 | 393,000 |
Changes of estimate | 1,476,000 | 1,022,000 |
Accretion expense | 2,551,000 | 1,055,000 |
Settlements | CAD 5,418,000 |  |
Minimum |  |  |
Other Long-term Liabilities |  |  |
Other liability repayment period | 5 years |  |
Accrual environmental cost | 2.20% |  |
Maximum |  |  |
Other Long-term Liabilities |  |  |
Other liability repayment period | 40 years |  |
Accrual environmental cost | 2.50% |  |
Environmental costs |  |  |
Other Long-term Liabilities |  |  |
Regulatory asset, expenditure recovery provided by regulator, time period | 7 years |  |
Amount of regulatory assets | CAD 103,761,000 | CAD 104,160,000 |
Empire |  |  |
Other Long-term Liabilities |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Asset Retirement Obligation | 31,717,000 |  |
Deerfield SponsorCo |  |  |
Other Long-term Liabilities |  |  |
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Asset Retirement Obligation | CAD 2,816,000 |  |

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