Financial and Other Derivative Instruments (Cumulative Gross Volume of Derivative Contracts Outstanding) (Details)	3 Months Ended
	Mar. 31, 2020 CAD ($) MWh MMBTU
Natural gas (MMBtu)
Derivative [Line Items]
Commodity, energy measures | MMBTU	1,756,620,693
Electricity (MWh)
Derivative [Line Items]
Commodity, energy measures	36,261,221
Foreign currency exchange (CAD)
Derivative [Line Items]
Commodity, monetary measure | $	$ 82,707,523
Renewable Energy Certificates (MWh)
Derivative [Line Items]
Commodity, energy measures	11,761,761