Information About Segments of Business Reconciliation of Assets from Segment to Consolidated (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item
Assets		$ 21,076.3	$ 19,327.1
General Insurance Group [Member]
Segment Reporting, Asset Reconciling Item
Assets		17,870.0	16,411.4
Title Insurance Group [Member]
Segment Reporting, Asset Reconciling Item
Assets		1,695.0	1,452.2
RFIG Run-off Business [Member]
Segment Reporting, Asset Reconciling Item
Assets		615.1	736.7
Total of major segments [Member]
Segment Reporting, Asset Reconciling Item
Assets		20,180.2	18,600.3
All Other Segments [Member]
Segment Reporting, Asset Reconciling Item
Assets	[1]	1,095.4	1,028.9
Business Intersegment, Eliminations [Member]
Segment Reporting, Asset Reconciling Item
Assets		$ (199.3)	$ (302.2)

[1] Includes amounts for a small life and accident insurance business as well as those of the parent holding company and its internal corporate services subsidiaries.