Other Long-Term Obligations (Detail) - CAD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020
Schedule of Other Liabilities [Line Items]
Employee retirement benefits	[1]	$ 2,036	$ 2,105
Asset retirement obligations and other environmental liabilities	[2]	1,680	1,676
Share-based incentive compensation liabilities		68	45
Operating lease liability	[3]	92	95
Other obligations		218	179
Total other long-term obligations		$ 4,094	$ 4,100

[1] Total recorded employee retirement benefits obligations also included $58 million in current liabilities (2020 - $58 million).

[2] Total asset retirement obligations and other environmental liabilities also included $100 million in current liabilities (2020 - $100 million).

[3] Total operating lease liability also included $82 million in current liabilities (2020 - $97 million). In addition to the total operating lease liability, additional undiscounted commitments for leases not yet commenced totalled $30 million (2020 - $27 million).