Schedule IV - Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 7,993.2	$ 7,358.2	[1]	$ 6,926.1	[1]
Ceded Premiums Earned	1,718.9	1,495.8	[1]	1,329.7	[1]
Assumed Premiums Earned	71.5	57.4	[1]	54.6	[1]
Net premiums earned	$ 6,345.8	$ 5,919.9	[1]	$ 5,651.1	[1]
Percentage of amount assumed to net	1.10%	1.00%	[1]	1.00%	[1]
Life Insurance in Force [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 1,665.7	$ 2,119.0		$ 3,383.2
Ceded Premiums Earned	936.8	1,135.9		1,865.4
Assumed Premiums Earned	0.0	0.0		0.0
Net premiums earned	$ 728.8	$ 983.0		$ 1,517.7
Percentage of amount assumed to net	0.00%	0.00%		0.00%
Life Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 7.8	$ 9.5		$ 11.9
Ceded Premiums Earned	2.4	3.8		5.0
Assumed Premiums Earned	0.0	0.0		0.0
Net premiums earned	$ 5.3	$ 5.7		$ 6.8
Percentage of amount assumed to net	0.00%	0.00%		0.00%
General Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 5,030.2	$ 4,857.0		$ 4,534.8
Ceded Premiums Earned	1,706.3	1,481.1		1,313.5
Assumed Premiums Earned	70.3	56.4		55.8
Net premiums earned	$ 3,394.2	$ 3,432.4		$ 3,277.1
Percentage of amount assumed to net	2.10%	1.60%		1.70%
Title Insurance Group [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 2,892.8	$ 2,412.8	[1]	$ 2,281.0	[1]
Ceded Premiums Earned	0.1	0.0	[1]	0.0	[1]
Assumed Premiums Earned	1.6	1.9	[1]	2.3	[1]
Net premiums earned	$ 2,894.4	$ 2,414.8	[1]	$ 2,283.3	[1]
Percentage of amount assumed to net	0.10%	0.10%	[1]	0.10%	[1]
RFIG Run-off Business [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 45.1	$ 59.2		$ 75.9
Ceded Premiums Earned	0.0	0.0		0.0
Assumed Premiums Earned	0.0	0.0		0.0
Net premiums earned	$ 45.1	$ 59.2		$ 75.9
Percentage of amount assumed to net	0.00%	0.00%		0.00%
Accident and health Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 17.1	$ 19.5		$ 22.3
Ceded Premiums Earned	10.4	11.8		14.5
Assumed Premiums Earned	0.0	0.0		0.0
Net premiums earned	$ 6.6	$ 7.6		$ 7.8
Percentage of amount assumed to net	0.00%	0.00%		0.00%
Life & Health Insurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 24.9	$ 29.0		$ 34.3
Ceded Premiums Earned	12.9	15.6		19.6
Assumed Premiums Earned	0.0	0.0		0.0
Net premiums earned	$ 12.0	$ 13.4		$ 14.6
Percentage of amount assumed to net	0.00%	0.00%		0.00%
Business Intersegment, Eliminations [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 0.0	$ 0.0		$ 0.0
Ceded Premiums Earned	(0.4)	(0.9)		(3.4)
Assumed Premiums Earned	(0.4)	(0.9)		(3.4)
Net premiums earned	$ 0.0	$ 0.0		$ 0.0
Percentage of amount assumed to net	0.00%	0.00%		0.00%

[1] Certain reclassifications were made to net premiums earned, title, escrow, and other fees, and underwriting, acquisition, and other expenses in 2019 and 2018 to conform to the presentation adopted in 2020.