Schedule IV - Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 6,936.7	$ 6,528.4	$ 6,296.6
Ceded Premiums Earned	1,495.8	1,329.7	1,264.5
Assumed Premiums Earned	57.4	54.6	48.1
Net amount	$ 5,498.3	$ 5,253.4	$ 5,080.2
Percentage of amount assumed to net	1.00%	1.00%	0.90%
Life Insurance in Force [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 2,119.0	$ 3,383.2	$ 4,860.6
Ceded Premiums Earned	1,135.9	1,865.4	2,552.5
Assumed Premiums Earned	0.0	0.0	0.0
Net amount	$ 983.0	$ 1,517.7	$ 2,308.0
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	$ 9.5	$ 11.9	$ 13.3
Ceded Premiums Earned	3.8	5.0	6.2
Assumed Premiums Earned	0.0	0.0	0.0
Net amount	$ 5.7	$ 6.8	$ 7.1
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	$ 4,857.0	$ 4,534.8	$ 4,307.5
Ceded Premiums Earned	1,481.1	1,313.5	1,246.4
Assumed Premiums Earned	56.4	55.8	49.7
Net amount	$ 3,432.4	$ 3,277.1	$ 3,110.8
Percentage of amount assumed to net	1.60%	1.70%	1.60%
Title Insurance Group [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 1,991.3	$ 1,883.3	$ 1,825.7
Ceded Premiums Earned	0.0	0.0	0.2
Assumed Premiums Earned	1.9	2.3	2.0
Net amount	$ 1,993.2	$ 1,885.6	$ 1,827.6
Percentage of amount assumed to net	0.10%	0.10%	0.10%
RFIG Run-off Business [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment
Gross amount	$ 59.2	$ 75.9	$ 123.5
Ceded Premiums Earned	0.0	0.0	0.5
Assumed Premiums Earned	0.0	0.0	0.0
Net amount	$ 59.2	$ 75.9	$ 122.9
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	$ 19.5	$ 22.3	$ 26.4
Ceded Premiums Earned	11.8	14.5	14.7
Assumed Premiums Earned	0.0	0.0	0.0
Net amount	$ 7.6	$ 7.8	$ 11.6
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	$ 29.0	$ 34.3	$ 39.8
Ceded Premiums Earned	15.6	19.6	20.9
Assumed Premiums Earned	0.0	0.0	0.0
Net amount	$ 13.4	$ 14.6	$ 18.8
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	(0.9)	(3.4)	(3.7)
Assumed Premiums Earned	(0.9)	(3.4)	(3.7)
Net amount	$ 0.0	$ 0.0	$ 0.0
Percentage of amount assumed to net	0.00%	0.00%	0.00%