Income Taxes (Summary of Income Tax Expense (Recovery)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Canadian:
Current tax expense	$ 74.3	$ 43.4	$ 60.9
Deferred tax expense	(5.7)	(2.7)	2.7
Foreign:
Current tax expense before application of operating loss carryforwards	132.3	100.2	29.6
Tax benefit of operating loss carryforwards	(0.1)	(1.4)	(4.0)
Total current tax expense	132.2	98.8	25.6
Deferred tax (benefit)	(63.5)	(63.1)	(3.0)
Total deferred tax (benefit)	(63.5)	(63.1)	(3.0)
Income tax expense	$ 137.3	$ 76.4	$ 86.2