Acquisitions, Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 44,695	$ 44,695
Impairment of goodwill	$ 0	$ 0
Weighted average period to amortize acquired intangible assets	13 years
Standard Commercial P & C Business Unit [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 2,100
Specialty Commercial Segment Member
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	17,400
MGA Commercial Products [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	19,900
Excess and Umbrella Business Unit [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	7,700
General Aviation and Satellite Component [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	9,700
Personal Lines Business Unit [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 5,300