Segment Information (Schedule of Information About Operations by Segment) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025		Mar. 31, 2024
Segment Reporting Information [Line Items]
Total revenues	$ 1,582.3		$ 1,424.6
Direct premiums and escrow fees	561.1		500.9
Agent premiums	654.6		563.8
Information and other	242.2		223.0
Net investment income (loss)	135.2		127.9
Net investment gains (losses)	(1.5)		(3.4)
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	1,582.3	[1]	1,425.1	[2]
Direct premiums and escrow fees	561.1		500.9
Agent premiums	654.6		563.8
Information and other	242.2		223.0
Net investment income (loss)	135.2		127.9
Net investment gains (losses)	(10.8)		9.0
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Total revenues	1,484.4	[1]	1,319.8	[2]
Direct premiums and escrow fees	459.6		403.2
Agent premiums	654.6		563.8
Information and other	236.0		217.2
Net investment income (loss)	137.7		116.7
Net investment gains (losses)	(3.5)		18.9
Operating Segments | Home Warranty
Segment Reporting Information [Line Items]
Total revenues	107.8	[1]	105.2	[2]
Direct premiums and escrow fees	101.6		97.7
Agent premiums	0.0		0.0
Information and other	6.2		5.9
Net investment income (loss)	0.8		0.9
Net investment gains (losses)	(0.8)		0.7
Operating Segments | Corporate and Eliminations
Segment Reporting Information [Line Items]
Total revenues	(9.9)		(0.4)
Direct premiums and escrow fees	(0.1)		0.0
Agent premiums	0.0		0.0
Information and other	0.0		(0.1)
Net investment income (loss)	(3.3)		10.3
Net investment gains (losses)	$ (6.5)		$ (10.6)

[1] Intersegment revenue is included within amounts shown.

[2] Intersegment revenue is included within amounts shown.