Deferred Acquisition Costs (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning balance	$ 10,201.4	$ 9,959.8	$ 10,187.6	$ 9,992.8
Costs deferred	1,151.9	1,105.6	2,208.0	2,269.5
Amortization	(973.3)	(926.9)	(2,015.6)	(2,123.8)
Ending balance	$ 10,380.0	$ 10,138.5	$ 10,380.0	$ 10,138.5

Amount of amortization expense (reversal of expense) for deferred policy acquisition costs.

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+ Details

- Definition

Amount of deferred policy acquisition cost capitalized on contract remaining in force.

+ References + Details