Schedule IV. Reinsurance (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 0	$ 0	$ 5,309,508
Ceded to Other Companies	0	0	1,014,794
Assumed From Other Companies	0	0	0
Net Amount	0	0	4,294,714
Total [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	1,133,583	1,083,981	1,107,828
Ceded to Other Companies	72,023	63,487	64,027
Assumed From Other Companies	25,412	16,957	15,059
Net Amount	$ 1,086,972	$ 1,037,451	$ 1,058,860
Percentage of Amount Assumed to Net Earned	2.34%	1.63%	1.42%
Continuing Operations - Property and Casualty Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 1,133,583	$ 1,083,981	$ 1,043,738
Ceded to Other Companies	72,023	63,487	61,305
Assumed From Other Companies	25,412	16,957	15,059
Net Amount	$ 1,086,972	$ 1,037,451	$ 997,492
Percentage of Amount Assumed to Net Earned	2.34%	1.63%	1.51%
Discontinued Operations | Discontinued Operations - Life, accident and health insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 0	$ 0	$ 64,090
Ceded to Other Companies	0	0	2,722
Assumed From Other Companies	0	0	0
Net Amount	$ 0	$ 0	$ 61,368
Percentage of Amount Assumed to Net Earned	0.00%	0.00%	0.00%