Schedule IV. Reinsurance (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 0	$ 5,309,508	$ 5,314,548
Ceded to Other Companies	0	1,014,794	1,023,197
Assumed From Other Companies	0	0	0
Net Amount	0	4,294,714	4,291,351
Total [Member]
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	1,083,981	1,107,828	1,067,128
Ceded to Other Companies	63,487	64,027	60,764
Assumed From Other Companies	16,957	15,059	17,037
Net Amount	$ 1,037,451	$ 1,058,860	$ 1,023,401
Percentage of Amount Assumed to Net Earned	1.63%	1.42%	1.66%
Continuing Operations - Property and Casualty Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 1,083,981	$ 1,043,738	$ 977,090
Ceded to Other Companies	63,487	61,305	57,996
Assumed From Other Companies	16,957	15,059	17,037
Net Amount	$ 1,037,451	$ 997,492	$ 936,131
Percentage of Amount Assumed to Net Earned	1.63%	1.51%	1.82%
Discontinued Operations | Discontinued Operations - Life, accident and health insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount	$ 0	$ 64,090	$ 90,038
Ceded to Other Companies	0	2,722	2,768
Assumed From Other Companies	0	0	0
Net Amount	$ 0	$ 61,368	$ 87,270
Percentage of Amount Assumed to Net Earned	0.00%	0.00%	0.00%