Regulatory Capital Restrictions (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018
Regulatory Capital Restrictions [Line Items]
Retained earnings, unappropriated	$ 63.7
Aggregate amount of shareholder dividends, maximum available next current fiscal year				$ 19.7
Hallmark (Payee) [Member]
Regulatory Capital Restrictions [Line Items]
Dividends paid by subsidiaries	$ 11.4	$ 10.5
Hallmark Insurance Company (Payer) [Member] | Hallmark (Payee) [Member]
Regulatory Capital Restrictions [Line Items]
Insurance agency management fee		1.1	$ 1.3
Subsidiaries [Member]
Regulatory Capital Restrictions [Line Items]
Statutory Accounting Practices, Future Dividend Payments Restrictions	lesser of 10% of prior year policyholders' surplus or prior year's net investment income
Subsidiaries [Member] | Subsequent Event [Member]
Regulatory Capital Restrictions [Line Items]
Aggregate amount of shareholder dividends, maximum available next current fiscal year				$ 27.6
American Hallmark Insurance Company and Texas Builders Insurance Company [Member]
Regulatory Capital Restrictions [Line Items]
Statutory Accounting Practices, Future Dividend Payments Restrictions	greater of statutory net income for the prior calendar year or 10% of statutory policyholders' surplus as of the prior year end
Hallmark Specialty Insurance Company [Member]
Regulatory Capital Restrictions [Line Items]
Statutory Accounting Practices, Future Dividend Payments Restrictions	greater of 10% of prior year policyholders' surplus or prior year's statutory net income, not including realized capital gains
Hallmark Insurance Company Subsidiaries [Member]
Regulatory Capital Restrictions [Line Items]
Amount of restricted net assets for consolidated and unconsolidated subsidiaries	$ 187.4
Statutory accounting practices, statutory capital and surplus, balance	233.3	248.4
Statutory accounting practices, statutory net income amount	$ 1.9	$ 8.7	$ 24.6