Goodwill and Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 11, 2007
Business Acquisition [Line Items]
Goodwill impairment	$ 0	$ 0	$ 0
Goodwill	181,831,000	181,831,000	181,831,000
Accumulated goodwill impairment losses	99,600,000	99,600,000
Identifiable intangibles not subject to amortization	31,164,000	31,164,000
Impairment of intangible assets	0	200,000	0
Amortization of intangible assets	597,000	597,000	597,000
Excess and Surplus Lines
Business Acquisition [Line Items]
Goodwill	181,831,000	181,831,000	181,831,000
Amortization of intangible assets	362,000	362,000	362,000
Specialty Admitted Insurance
Business Acquisition [Line Items]
Goodwill	0	0	0
Impairment of intangible assets		200,000
Amortization of intangible assets	$ 235,000	235,000	$ 235,000
James River Group, Inc.
Business Acquisition [Line Items]
Percentage of outstanding shares acquired				100.00%
State Licenses
Business Acquisition [Line Items]
Identifiable intangibles not subject to amortization		$ 0