Debt Securities (Sales of Debt Securities) (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Debt Securities, Available-for-Sale [Line Items]
Realized losses on sales of debt securities	$ 3.2	$ 6.8	$ 5.7	$ 9.4
Realized gains on sales of debt securities	1.7	1.4	2.9	2.5
Proceeds from sales of debt securities	$ 276.4	$ 240.2	$ 543.7	$ 507.0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details