Offsetting of Assets and Liabilities (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Offsetting Assets and Liabilities [Line Items]
Collateral received	$ 14.3	$ 5.0
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	592.2	190.9
Collateral deposited with derivative counterparties for derivatives instruments with credit-risk-related contingent features that are in a liability position	548.9	55.1
Net maximum amount of termination payments that could have been required	43.3	135.8
Net Investment Hedges
Offsetting Assets and Liabilities [Line Items]
Collateral received	67.7
Gross amounts not offset in the balance sheet	$ 473.4
Cash collateral received from derivative counterparties and not offset against derivative assets		131.8
Cash collateral deposited with derivative counterparties not offset against derivative liabilities		$ 26.3