Reinsurance and Catastrophes - Effects of Reinsurance (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	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, 2020	Dec. 31, 2019	Dec. 31, 2018
Gross Amount
Premiums written and contract deposits, Gross Amount													$ 1,369,897	$ 1,337,847	$ 1,255,557
Premiums and contract charges earned, Gross Amount													949,525	917,610	841,147
Benefits, claims and settlement expenses, Gross Amount													475,746	633,874	769,664
Ceded to Other Companies
Premiums written and contract deposits, Ceded to Other Companies													20,388	23,872	28,773
Premiums and contract charges earned, Ceded to Other Companies													28,757	30,412	28,837
Benefits, claims and settlement expenses, Ceded to Other Companies													(86,184)	56,325	136,601
Assumed from Other Companies
Premiums written and contract deposits, Assumed from Other Companies													9,830	10,567	8,259
Premiums and contract charges earned, Assumed from Other Companies													9,929	10,756	5,023
Benefits, claims and settlement expenses, Assumed from Other Companies													6,961	7,519	4,497
Net Amount
Premiums written and contract deposits, Net Amount	$ 332,559	$ 368,853	$ 329,169	$ 328,758	$ 346,242	$ 371,216	$ 311,691	$ 295,394	$ 311,216	$ 338,097	$ 301,722	$ 284,008	1,359,339	1,324,542	1,235,043
Premiums and contract charges earned, Net Amount	$ 233,648	$ 235,353	$ 225,431	$ 236,265	$ 240,392	$ 239,681	$ 208,096	$ 209,785	$ 201,905	$ 206,820	$ 205,610	$ 202,998	930,697	897,954	817,333
Benefits, claims and settlement expenses													$ 568,891	$ 585,068	$ 637,560