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Commitments and Contingent Liabilities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Jul. 31, 2017
Commitments and Contingent Liabilities [Line Items]
Litigation and regulatory matters loss contingency, range of possible loss, maximum (less than)	$ 100.0
Indonesia \| CT Corp Joint Venture
Commitments and Contingent Liabilities [Line Items]
Joint Venture with CT Corp, Ownership Percentage				49.00%
Commitments \| Commercial mortgage loans
Commitments and Contingent Liabilities [Line Items]
Total outstanding mortgage loan commitments	176.0		$ 270.0
Allowance for credit losses	0.2		0.3
Change in allowance for credit loss expense (reversal)	0.1	$ 0.0
Commitments \| Investments
Commitments and Contingent Liabilities [Line Items]
Commitments to purchase investment (excluding commercial mortgage loans)	1,162.0		1,182.0
Purchase Commitment
Commitments and Contingent Liabilities [Line Items]
Change in allowance for credit loss expense (reversal)	0.0	$ 0.0
Other Guarantees
Commitments and Contingent Liabilities [Line Items]
Accrued liabilities	$ 32.0		$ 32.0