Schedule III and VI Supplementary Insurance Information Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	$ 298,742	$ 257,826	$ 267,580
Future policy benefits, claims and claim expenses	6,107,907	5,921,484	5,777,857
Unearned premiums	276,225	260,539	246,274
Other policy claims and benefits payable	767,988	724,261	708,950
Premium revenue/ premium earned	817,333	794,703	759,146
Net investment income	376,507	373,630	361,186
Benefits, claims and settlement expenses	843,759	780,941	733,026
Amortization of deferred policy acquisition costs	109,889	102,185	96,732
Other operating expenses	218,414	199,737	184,920
Property and Casualty
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	30,033	29,191	27,604
Future policy benefits, claims and claim expenses	367,180	319,182	307,757
Discount, if any, deducted in previous column	0	0	0
Unearned premiums	274,351	258,502	244,005
Other policy claims and benefits payable	0	0	0
Premium revenue/ premium earned	665,734	648,263	620,514
Net investment income	40,104	36,178	38,997
Benefits, claims and settlement expenses	547,659	496,289	464,098
Claims and claims adjustment expense incurred related to current year	547,959	498,989	471,098
Claims and claims adjustment expense incurred related to prior years	(300)	(2,700)	(7,000)
Amortization of deferred policy acquisition costs	79,073	76,967	74,950
Other operating expenses	101,834	96,488	90,802
Paid claims and claim adjustment expenses	531,977	481,074	468,778
Premiums written	681,583	662,760	634,319
Retirement
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	209,232	174,661	188,117
Future policy benefits, claims and claim expenses	4,573,170	4,466,039	4,372,062
Unearned premiums	704	705	671
Other policy claims and benefits payable	764,607	720,926	705,603
Premium revenue/ premium earned	31,269	28,003	24,937
Net investment income	262,634	261,994	249,410
Benefits, claims and settlement expenses	168,732	159,385	151,185
Amortization of deferred policy acquisition costs	23,186	17,759	14,635
Other operating expenses	57,269	49,733	40,289
Life
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Deferred policy acquisition costs	59,477	53,974	51,859
Future policy benefits, claims and claim expenses	1,167,557	1,136,263	1,098,038
Unearned premiums	1,170	1,332	1,598
Other policy claims and benefits payable	3,381	3,335	3,347
Premium revenue/ premium earned	120,330	118,437	113,695
Net investment income	74,399	76,195	73,567
Benefits, claims and settlement expenses	127,368	125,267	117,743
Amortization of deferred policy acquisition costs	7,630	7,459	7,147
Other operating expenses	36,314	36,550	36,806
Other, including consolidating eliminations | Eliminations
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information [Line Items]
Net investment income	(630)	(737)	(788)
Other operating expenses	$ 22,997	$ 16,966	$ 17,023