Schedule III and VI Supplementary Insurance Information Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 276,668	$ 298,742	$ 257,826
Future policy benefits, claims and claim expenses	6,677,306	6,107,907	5,921,484
Unearned premiums	279,163	276,225	260,539
Other policy claims and benefits payable	647,283	767,988	724,261
Premium revenue/ premium earned	897,954	817,333	794,703
Net investment income	365,064	376,507	373,630
Benefits, claims and settlement expenses	797,854	843,759	780,941
Amortization of deferred policy acquisition costs	109,181	109,889	102,185
Other operating expenses	287,001	218,414	199,737
Property and Casualty
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	28,616	30,033	29,191
Future policy benefits, claims and claim expenses	386,976	367,180	319,182
Discount, if any, deducted in previous column	0	0	0
Unearned premiums	273,998	274,351	258,502
Other policy claims and benefits payable	0	0	0
Premium revenue/ premium earned	683,454	665,734	648,263
Net investment income	41,740	40,104	36,178
Benefits, claims and settlement expenses	475,563	547,659	496,289
Claims and claims adjustment expense incurred related to current year	483,062	547,959	498,989
Claims and claims adjustment expense incurred related to prior years	(7,500)	(300)	(2,700)
Amortization of deferred policy acquisition costs	79,453	79,073	76,967
Other operating expenses	105,489	101,834	96,488
Paid claims and claim adjustment expenses	486,547	531,977	481,074
Premiums written	683,101	681,583	662,760
Supplemental
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	1,967
Future policy benefits, claims and claim expenses	390,276
Unearned premiums	3,218
Other policy claims and benefits payable	0
Premium revenue/ premium earned	65,815
Net investment income	7,480
Benefits, claims and settlement expenses	24,723
Amortization of deferred policy acquisition costs	438
Other operating expenses	26,476
Retirement
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	185,294	209,232	174,661
Future policy benefits, claims and claim expenses	4,698,461	4,573,170	4,466,039
Unearned premiums	734	704	705
Other policy claims and benefits payable	643,826	764,607	720,926
Premium revenue/ premium earned	29,083	31,269	28,003
Net investment income	245,475	262,634	261,994
Benefits, claims and settlement expenses	173,116	168,732	159,385
Amortization of deferred policy acquisition costs	21,446	23,186	17,759
Other operating expenses	90,782	57,269	49,733
Life
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	60,791	59,477	53,974
Future policy benefits, claims and claim expenses	1,201,593	1,167,557	1,136,263
Unearned premiums	1,213	1,170	1,332
Other policy claims and benefits payable	3,457	3,381	3,335
Premium revenue/ premium earned	119,602	120,330	118,437
Net investment income	71,957	74,399	76,195
Benefits, claims and settlement expenses	124,452	127,368	125,267
Amortization of deferred policy acquisition costs	7,844	7,630	7,459
Other operating expenses	37,820	36,314	36,550
Other, including consolidating eliminations | Eliminations
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Net investment income	(1,588)	(630)	(737)
Other operating expenses	$ 26,434	$ 22,997	$ 16,966