Schedule VI. Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Net Realized Investment Gains (Losses)	$ (32,395)	$ 53,779	$ (20,179)
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	887,119	835,507	785,778
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(17,652)	(5,335)	(54,167)
Consolidated Property and Casualty Insurance Entity
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Deferred Policy Acquisition Costs	87,094	94,292	92,796
Reserves for Unpaid Claims and Claim Adjustment Expenses	1,578,131	1,421,754	1,312,483
Unearned Premiums	464,845	505,162	492,928
Earned Premiums	1,055,082	1,086,972	1,037,451
Net Realized Investment Gains (Losses)	(32,395)	53,779	(20,179)
Net Investment Income	39,670	60,414	52,894
Claims and Claim Adjustment Expenses Incurred Related to: Current Year	887,119	835,507	785,778
Claims and Claim Adjustment Expenses Incurred Related to: Prior Years	(17,652)	(5,335)	(54,167)
Amortization of Deferred Policy Acquisition Costs	210,252	216,699	206,232
Paid Claims and Claim Adjustment Expenses	776,397	732,343	640,534
Premiums Written	$ 1,011,350	$ 1,096,730	$ 1,061,664