Loss and Loss Adjustment Expense Reserves - Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses
Net outstanding liabilities	$ 445,252
Reinsurance recoverable on unpaid claims	83,724	$ 68,261	$ 61,245
Unallocated claims adjustment expenses	31,345
Total gross liability for unpaid claims and claim adjustment expenses	560,321	$ 553,977	$ 482,012	$ 455,014
Private Passenger Automobile
Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses
Net outstanding liabilities	229,343
Reinsurance recoverable on unpaid claims	1,815
Commercial Automobile
Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses
Net outstanding liabilities	73,049
Reinsurance recoverable on unpaid claims	60,852
Homeowners
Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses
Net outstanding liabilities	75,455
Reinsurance recoverable on unpaid claims	10,379
Other short-Duration Insurance Lines
Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Liability for Unpaid claims and Claim Adjustment Expenses
Net outstanding liabilities	67,405
Reinsurance recoverable on unpaid claims	$ 10,678