Schedule III - Supplementary Insurance Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule III - Supplementary Insurance Information
Deferred Policy Acquisition Costs	$ 74,287	$ 73,355	$ 72,202
Future Policy Benefits, Losses, Claims and Loss Expenses	610,566	584,719	574,054
Unearned Premiums	442,219	435,380	428,257
Earned Premiums	788,777	781,587	774,420
Premium Revenue	788,777	781,587	774,420
Net Investment Income	46,665	43,788	38,758
Benefits, Claims, Losses, and Settlement Expenses	509,846	485,513	503,887
Amortization of Deferred Policy Acquisition Costs	147,945	146,601	144,703
Other Operating Expenses	96,191	100,042	103,733
Premiums Written	$ 794,409	$ 786,912	$ 781,054