Losses And Loss Adjustment Expense Reserves - Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	$ 1,196,434
Reinsurance recoverable on unpaid claims	13,160
Insurance lines other than short-duration	1,480
Unallocated claims adjustment expenses	79,174
Unallocated claims adjustment expenses, aggregate reconciling items	80,654
Total gross loss and loss adjustment expense reserves	1,290,248	$ 1,146,688	$ 1,091,797	$ 1,038,984
Property insurance product line, automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	1,016,832
Reinsurance recoverable on unpaid claims	12,601
Property insurance product line, homeowners' [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	116,050
Reinsurance recoverable on unpaid claims	199
Property Insurance Product Line, WAIC Automobile [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	12,232
Other Short-duration Insurance Product Line [Member]
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	51,320
Reinsurance recoverable on unpaid claims	$ 360