Equity Securities (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Schedule Of Investments [Line Items]
Realized and unrealized net gains (losses) on equity securities	$ 4.3	$ 54.9
Net unrealized gains (losses) on equity securities	0.9	51.2
Common Stock
Schedule Of Investments [Line Items]
Net unrealized gains (losses) on equity securities	$ 37.9
Common Stock | Offerpad Inc [Member]
Schedule Of Investments [Line Items]
Net unrealized gains (losses) on equity securities		$ 12.7