Basis of Presentation and Significant Accouting Policies (Basis of Presentation) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	May 11, 2018	Jul. 31, 2012
Basis of Presentation
ROU lease asset	$ 21.5
Operating lease liability	$ 21.8
HG Global
Basis of Presentation
Percentage of par value of policy reinsured	15.00%
Surplus notes	$ 481.3				$ 503.0
Preferred Stock | HG Global
Basis of Presentation
Ownership interest (as a percent)	96.90%		96.90%
Common Stock | HG Global
Basis of Presentation
Ownership interest (as a percent)	88.40%		88.40%
NSM Insurance HoldCo, LLC
Basis of Presentation
Ownership interest (as a percent)	95.30%		95.50%	95.00%
Fully diluted ownership interest (as a percent)	84.80%		85.00%
Accounting Standards Update 2016-02
Basis of Presentation
ROU lease asset	$ 21.5	$ 23.2
Operating lease liability	$ 21.8	$ 23.2