Statutory Accounting and Regulation - Schedule of Affiliates' Surplus Regarding Policyholders (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices
Statutory capital and surplus required (percent of total liabilities)	10.00%
FLORIDA
Statutory Accounting Practices
Statutory Accounting Practices, Statutory Capital and Surplus Required, Dollar Limit	$ 10,000
United Property & Casualty Insurance Company
Statutory Accounting Practices
Statutory capital and surplus balance	167,127	$ 164,281
Family Security Insurance Company
Statutory Accounting Practices
Statutory capital and surplus balance	25,019	22,038
Interboro Insurance Company
Statutory Accounting Practices
Statutory capital and surplus balance	43,190	42,827
American Coastal Insurance Company
Statutory Accounting Practices
Statutory capital and surplus balance	166,988	$ 160,238
Minimum | United Property & Casualty Insurance Company | FLORIDA
Statutory Accounting Practices
Statutory capital and surplus required	43,448
Minimum | Family Security Insurance Company | HAWAII
Statutory Accounting Practices
Statutory capital and surplus required	3,250
Minimum | Interboro Insurance Company | NEW YORK
Statutory Accounting Practices
Statutory capital and surplus required	4,700
Minimum | American Coastal Insurance Company | FLORIDA
Statutory Accounting Practices
Statutory capital and surplus required	$ 16,168