Income Taxes (Deferred Tax Assets (Liabilities) Resulting From Temporary Differences) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Tax loss and deduction carryforwards	$ 1,997.5	$ 2,111.5
Tax credit carryforwards	119.0	658.3
All other future deductions	435.7	485.5
Valuation allowance	(2,327.6)	(2,960.0)
Total deferred tax assets	224.6	295.3
Deferred tax liabilities:
Total deferred tax liabilities	(90.8)	(142.2)
Net deferred tax assets	$ 133.8	$ 153.1