Segment Information (Schedule of Information About Operations by Segment) (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2025		Jun. 30, 2024		Jun. 30, 2025		Jun. 30, 2024
Segment Reporting Information [Line Items]
Total revenues	$ 1,841.3		$ 1,612.3		$ 3,423.6		$ 3,036.9
Direct premiums and escrow fees	704.2		632.7		1,265.3		1,133.6
Agent premiums	716.5		616.3		1,371.1		1,180.1
Information and other	270.1		246.6		512.3		469.6
Net investment income (loss)	160.2		129.9		295.4		257.8
Net investment gains (losses)	(5.4)		(1.0)		(6.9)		(4.4)
Operating Segments
Segment Reporting Information [Line Items]
Total revenues	1,841.4	[1]	1,612.9	[2]	3,423.7	[3]	3,038.0	[4]
Direct premiums and escrow fees	704.2		632.7		1,265.3		1,133.6
Agent premiums	716.5		616.3		1,371.1		1,180.1
Information and other	270.1		246.6		512.3		469.6
Net investment income (loss)	160.2		129.9		295.4		257.8
Net investment gains (losses)	(9.7)		(13.2)		(20.5)		(4.2)
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Total revenues	1,722.9	[1]	1,521.9	[2]	3,207.3	[3]	2,841.7	[4]
Direct premiums and escrow fees	600.4		533.0		1,060.0		936.2
Agent premiums	716.5		616.3		1,371.1		1,180.1
Information and other	264.3		240.9		500.3		458.1
Net investment income (loss)	147.1		125.7		284.8		242.4
Net investment gains (losses)	(5.4)		6.0		(8.9)		24.9
Operating Segments | Home Warranty
Segment Reporting Information [Line Items]
Total revenues	110.2	[1]	106.8	[2]	218.0	[3]	212.0	[4]
Direct premiums and escrow fees	103.7		99.6		205.3		197.3
Agent premiums	0.0		0.0		0.0		0.0
Information and other	5.9		5.8		12.1		11.7
Net investment income (loss)	1.2		1.1		2.0		2.0
Net investment gains (losses)	(0.6)		0.3		(1.4)		1.0
Operating Segments | Corporate and Eliminations
Segment Reporting Information [Line Items]
Total revenues	8.2		(16.4)		(1.7)		(16.8)
Direct premiums and escrow fees	(0.1)		0.1		0.0		0.1
Agent premiums	0.0		0.0		0.0		0.0
Information and other	(0.1)		(0.1)		(0.1)		(0.2)
Net investment income (loss)	11.9		3.1		8.6		13.4
Net investment gains (losses)	$ (3.7)		$ (19.5)		$ (10.2)		$ (30.1)

[1] Intersegment revenue is included within amounts shown.

[2] Intersegment revenue is included within amounts shown.

[3] Intersegment revenue is included within amounts shown.

[4] Intersegment revenue is included within amounts shown.