Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Net Realized Investment Gains (Losses)	$ 53,779	$ (20,179)	$ 4,055
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	835,507	785,778	779,966
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(5,335)	(54,167)	(54,253)
Consolidated Property and Casualty Insurance Entity
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Deferred Policy Acquisition Costs	94,292	92,796	88,102
Reserves for Unpaid Claims and Claim Adjustment Expenses	1,421,754	1,312,483	1,124,183
Unearned Premiums	505,162	492,928	465,391
Earned Premiums	1,086,972	1,037,451	997,492
Net Realized Investment Gains (Losses)	53,779	(20,179)	4,055
Net Investment Income	60,414	52,894	51,190
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	835,507	785,778	779,966
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(5,335)	(54,167)	(54,253)
Amortization of Deferred Policy Acquisition Costs	216,699	206,232	207,746
Paid Claims and Claim Adjustment Expenses	732,343	640,534	625,503
Premiums Written	$ 1,096,730	$ 1,061,664	$ 1,019,113