Property Sale (Details) - Chicago property and easements $ in Millions	3 Months Ended
	Mar. 31, 2021 CAD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from exchanged property and property easements	$ 103
Cash proceeds from properties and easements	61
Property assets, Fair value acquired	42
Gain on exchange of properties and easements	50
Gain on exchange of property and easements, after tax	38
Deferred gain on exchange of property and easements	$ 53