Property and Casualty Unpaid Claims and Claim Expenses - Reconciliation of Net Incurred and Paid Claims (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Liability for Claims and Claims Adjustment Expense, Total	$ 347,749	$ 329,888
Property, Liability and Casualty Insurance Product Line [Member]
Reinsurance Recoverables, Including Reinsurance Premium Paid	57,409
Short-duration Insurance Contracts, Liability for Unpaid Claims and Claims Adjustment Expense, Accumulated Unallocated Claim Adjustment Expense	23,046
Liability For Other Than Short Duration And Unallocated Claims Adjustment Expenses	51,613
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	238,727
Property, Liability and Casualty Insurance Product Line [Member] | Homeowners
Reinsurance Recoverables, Including Reinsurance Premium Paid	298
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	30,302
Property, Liability and Casualty Insurance Product Line [Member] | Auto liability
Reinsurance Recoverables, Including Reinsurance Premium Paid	50,713
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	195,636
Property, Liability and Casualty Insurance Product Line [Member] | Auto physical damage
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	10,066
Property, Liability and Casualty Insurance Product Line [Member] | Other Short Duration Lines [Member]
Reinsurance Recoverables, Including Reinsurance Premium Paid	6,398
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,723
Property, Liability and Casualty Insurance Product Line [Member] | Other Than Short Duration Line [Member]
Prior years paid	$ 28,567