Segment Financial Information (Schedule of Information About Revenues by Segment) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
Segment Reporting Information [Line Items]
Revenues	$ 6,128.1		$ 6,003.5		$ 7,605.2
Direct premiums and escrow fees	2,446.0		2,252.1		3,084.8
Agent premiums	2,561.9		2,449.3		3,547.6
Information and other	960.8		938.5		1,148.5
Net investment income	561.0		570.0		340.1
Net investment gains (losses)	(335.1)		(80.9)		(85.4)
Operating Segments
Segment Reporting Information [Line Items]
Revenues	6,129.6	[1]	6,004.8	[2]	7,607.7	[3]
Direct premiums and escrow fees	2,446.0		2,252.1		3,084.8
Agent premiums	2,561.9		2,449.3		3,547.6
Information and other	960.8		938.5		1,148.5
Net investment income	561.0		570.0		340.1
Net investment gains (losses)	(401.6)		(206.4)		(515.8)
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Revenues	5,737.3	[1]	5,724.8	[2]	7,546.9	[3]
Direct premiums and escrow fees	2,048.3		1,856.4		2,662.9
Agent premiums	2,561.9		2,449.3		3,547.6
Information and other	938.2		917.1		1,127.1
Net investment income	534.3		540.2		359.1
Net investment gains (losses)	(345.4)		(38.2)		(149.8)
Operating Segments | Home Warranty
Segment Reporting Information [Line Items]
Revenues	425.7	[1]	417.2	[2]	419.0	[3]
Direct premiums and escrow fees	397.8		395.6		413.1
Agent premiums	0.0		0.0		0.0
Information and other	22.5		21.7		13.3
Net investment income	4.0		5.9		5.1
Net investment gains (losses)	1.4		(6.0)		(12.5)
Operating Segments | Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenues	(34.9)		(138.5)		(360.7)
Direct premiums and escrow fees	(0.1)		0.1		8.8
Agent premiums	0.0		0.0		0.0
Information and other	0.1		(0.3)		8.1
Net investment income	22.7		23.9		(24.1)
Net investment gains (losses)	(57.6)		(162.2)		(353.5)
Operating Segments | Corporate
Segment Reporting Information [Line Items]
Revenues	(33.4)	[1]	(137.2)	[2]	(358.2)	[3]
Eliminations
Segment Reporting Information [Line Items]
Revenues	$ (1.5)		$ (1.3)		$ (2.5)

[1] Intersegment revenue is included within amounts shown.

[2] Intersegment revenue is included within amounts shown.

[3] Intersegment revenue is included within amounts shown.