Debt (Other Credit Facilities) (Narrative) (Details) $ in Millions	Dec. 31, 2020 USD ($)	Dec. 31, 2020 CAD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 CAD ($)
Debt Instrument [Line Items]
Letters of credit issued	$ 151.8		$ 115.1
Other Credit Facilities [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	15.7	$ 20,000,000.0	15.4	$ 20,000,000.0
Long-term debt obligations		$ 0		$ 0
Line of Credit [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Letters of credit issued	18.2		$ 17.1
Line of Credit [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50.0
Line of Credit [Member] | Letter of Credit [Member] | Standby Letters of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	0.50%	0.50%	0.40%	0.40%