Equity Securities (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Schedule Of Investments [Line Items]
Realized and unrealized net gains (losses) on equity securities	$ 10.9	$ 12.4
Net unrealized gains on equity securities	10.5	11.7
Cash proceeds from sale of equity securities	44.2	$ 11.1
Common Stock | Offerpad Inc [Member]
Schedule Of Investments [Line Items]
Net unrealized gains on equity securities	$ 11.0