Segment Financial Information (Schedule of Selected Financial Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Revenues	$ 6,003.5	$ 7,605.2	$ 9,220.8
Depreciation and amortization	188.5	167.5	158.4
Income (loss) before income taxes	274.4	325.7	1,641.3
Assets	16,802.8	14,955.3	16,451.3
Capital expenditures	278.7	274.9	172.1
Direct premiums and escrow fees	2,252.1	3,084.8	3,598.4
Agent premiums	2,449.3	3,547.6	3,757.1
Information and other	938.5	1,148.5	1,214.9
Net investment income	570.0	340.1	214.8
Realized (losses) gains of net investment	(80.9)	(85.4)	20.3
Operating Segments
Segment Reporting Information [Line Items]
Revenues		7,605.2	9,220.8
Direct premiums and escrow fees		3,084.8	3,598.4
Agent premiums		3,547.6	3,757.1
Information and other		1,148.5	1,214.9
Net investment income		340.1	214.8
Realized (losses) gains of net investment	(206.4)	(515.8)	435.6
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Revenues	5,724.8	7,546.9	8,321.0
Depreciation and amortization	183.6	162.3	152.5
Income (loss) before income taxes	494.0	757.4	1,358.7
Assets	15,768.2	13,911.2	15,058.8
Capital expenditures	271.1	271.3	168.5
Direct premiums and escrow fees	1,856.4	2,662.9	3,100.9
Agent premiums	2,449.3	3,547.6	3,757.1
Information and other	917.1	1,127.1	1,203.1
Net investment income	540.2	359.1	188.3
Realized (losses) gains of net investment	(38.2)	(149.8)	71.6
Operating Segments | Home Warranty
Segment Reporting Information [Line Items]
Revenues	417.2	419.0	421.9
Depreciation and amortization	4.8	5.1	5.8
Income (loss) before income taxes	54.3	44.6	52.6
Assets	351.9	389.7	436.4
Capital expenditures	7.6	3.6	3.6
Direct premiums and escrow fees	395.6	413.1	399.8
Agent premiums	0.0	0.0	0.0
Information and other	21.7	13.3	10.9
Net investment income	5.9	5.1	4.1
Realized (losses) gains of net investment	(6.0)	(12.5)	7.1
Operating Segments | Corporate and Eliminations
Segment Reporting Information [Line Items]
Revenues	(138.5)	(360.7)	477.9
Depreciation and amortization	0.1	0.1	0.1
Income (loss) before income taxes	(273.9)	(476.3)	230.0
Assets	682.7	654.4	956.1
Capital expenditures	0.0	0.0	0.0
Direct premiums and escrow fees	0.1	8.8	97.7
Agent premiums	0.0	0.0	0.0
Information and other	(0.3)	8.1	0.9
Net investment income	23.9	(24.1)	22.4
Realized (losses) gains of net investment	$ (162.2)	$ (353.5)	$ 356.9