Offsetting of Assets and Liabilities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Offsetting Assets and Liabilities [Line Items]
Collateral received	$ 10.3	$ 12.2
Gross amounts not offset in the balance sheet	0.0	0.0
Aggregate fair value of all derivative instruments with credit-risk-related contingent features that are in a liability position	1,200.0	1,200.0
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	929.3	1,100.0
Net maximum amount of termination payments that could have been required	270.9	52.2
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Collateral received	140.3
Gross amounts not offset in the balance sheet	$ 10.0
Cash collateral received from derivative counterparties and not offset against derivative assets		373.1
Cash collateral deposited with derivative counterparties not offset against derivative liabilities		$ 21.3