Information About Segments of Business Reconciliation of Assets from Segment to Consolidated (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting, Asset Reconciling Item
Assets	$ 18,905.4	$ 18,591.6
General Insurance Group [Member]
Segment Reporting, Asset Reconciling Item
Assets	15,546.1	15,305.7
Title Insurance Segment [Member]
Segment Reporting, Asset Reconciling Item
Assets	1,438.9	1,423.0
RFIG Run-off Business [Member]
Segment Reporting, Asset Reconciling Item
Assets	887.7	904.8
Total Company Segments [Member]
Segment Reporting, Asset Reconciling Item
Assets	17,872.8	17,633.6
All Other Segments [Member]
Segment Reporting, Asset Reconciling Item
Assets	1,353.1	1,301.8
Intersegment Elimination [Member]
Segment Reporting, Asset Reconciling Item
Assets	$ (320.5)	$ (343.9)