Segment Information (Schedule of Reportable Segment Performance Significant Expenses and Assets) (Parenthetical) (Detail) - USD ($) $ in Millions	Jun. 30, 2025		Dec. 31, 2024	Jun. 30, 2024
Segment Reporting Information [Line Items]
Cash balance	$ 2,031.2		$ 1,718.1
Total assets	16,273.9		$ 14,908.6	$ 15,157.3
Eliminations
Segment Reporting Information [Line Items]
Cash balance	(139.9)			(83.7)
Receivable from subsidiary	(19.5)			(42.3)
Total assets	(162.9)	[1]		(177.4)	[2]
Eliminations | Home Warranty
Segment Reporting Information [Line Items]
Cash balance	$ (3.5)			(1.9)
Receivable from subsidiary				$ (49.5)

[1] Elimination of intercompany asset balances: Holding company cash balances also included in the title insurance and services segment   $ (139.9 ) Home warranty segment cash balances also included in the title insurance and services segment     (3.5 ) Holding company receivable from a subsidiary within the title insurance and services segment     (19.5 )     $ (162.9 )   For the three months ended June 30, 2024:

[2] Elimination of intercompany asset balances: Holding company cash balances also included in the title insurance and services segment   $ (83.7 ) Home warranty segment cash balances also included in the title insurance and services segment     (1.9 ) Holding company receivable from a subsidiary within the home warranty segment     (49.5 ) Holding company receivable from a subsidiary within the title insurance and services segment     (42.3 )     $ (177.4 )