Reinsurance and Catastrophes - Effects of Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gross Amount
Premiums written and contract deposits, Gross Amount													$ 1,337,847	$ 1,255,557	$ 1,244,500
Premiums and contract charges earned, Gross Amount													917,610	841,147	812,099
Benefits, claims and settlement expenses, Gross Amount													633,874	769,664	588,621
Ceded to Other Companies
Premiums written and contract deposits, Ceded to Other Companies													23,872	28,773	21,989
Premiums and contract charges earned, Ceded to Other Companies													30,412	28,837	22,036
Benefits, claims and settlement expenses, Ceded to Other Companies													56,325	136,601	10,472
Assumed from Other Companies
Premiums written and contract deposits, Assumed from Other Companies													10,567	8,259	4,606
Premiums and contract charges earned, Assumed from Other Companies													10,756	5,023	4,640
Benefits, claims and settlement expenses, Assumed from Other Companies													7,519	4,497	4,157
Net Amount
Premiums written and contract deposits, Net Amount													1,324,542	1,235,043	1,227,117
Premiums and contract charges earned, Net Amount	$ 240,392	$ 239,681	$ 208,096	$ 209,785	$ 201,905	$ 206,820	$ 205,610	$ 202,998	$ 204,328	$ 198,935	$ 195,718	$ 195,722	897,954	817,333	794,703
Benefits, claims and settlement expenses													$ 585,068	$ 637,560	$ 582,306