Schedule III and VI Supplementary Insurance Information Supplemental Information Concerning Property and Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Deferred policy acquisition costs	$ 248,000	$ 229,800	$ 276,700
Future policy benefits, claims and claim expenses	7,003,700	6,884,100	6,677,300
Unearned premiums	255,100	264,500	279,200
Other policy claims and benefits payable	945,900	751,300	647,300
Premium revenue/ premium earned	889,600	930,700	898,000
Net investment income	422,500	357,600	365,100
Benefits, claims and settlement expenses	782,100	773,500	797,900
Amortization of deferred policy acquisition costs	94,700	99,900	109,200
Other operating expenses	278,400	277,400	287,000
Eliminations
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Net investment income	(2,400)	(2,400)	(1,600)
Other operating expenses	24,400	20,700	26,400
Property & Casualty
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Deferred policy acquisition costs	24,400	26,100	28,600
Future policy benefits, claims and claim expenses	362,400	372,100	387,000
Discount, if any, deducted in previous column	0	0	0
Unearned premiums	249,800	259,400	274,000
Other policy claims and benefits payable	0	0	0
Premium revenue/ premium earned	617,400	650,100	683,500
Net investment income	61,100	42,600	41,700
Benefits, claims and settlement expenses	447,900	431,000	475,600
Claims and claims adjustment expense incurred related to current year	455,100	441,200	483,100
Claims and claims adjustment expense incurred related to prior years	(7,200)	(10,200)	(7,500)
Amortization of deferred policy acquisition costs	67,700	74,400	79,400
Other operating expenses	97,200	97,700	105,500
Paid claims and claim adjustment expenses	455,100	438,200	486,600
Premiums written	607,800	635,500	683,100
Supplemental
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Deferred policy acquisition costs	4,200	4,300
Future policy benefits, claims and claim expenses	393,900	392,400
Unearned premiums	3,100	3,100
Other policy claims and benefits payable	72,500	41,500
Premium revenue/ premium earned	125,300	130,700
Net investment income	24,800	17,800
Benefits, claims and settlement expenses	40,000	43,100
Amortization of deferred policy acquisition costs	1,100	1,300
Other operating expenses	52,500	51,700
Retirement
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Deferred policy acquisition costs	153,800	137,700	185,300
Future policy benefits, claims and claim expenses	4,967,700	4,874,200	4,698,400
Unearned premiums	700	700	800
Other policy claims and benefits payable	869,800	706,300	643,800
Premium revenue/ premium earned	38,500	29,700	29,100
Net investment income	255,900	229,800	245,500
Benefits, claims and settlement expenses	166,300	164,800	173,100
Amortization of deferred policy acquisition costs	18,500	16,800	21,500
Other operating expenses	67,500	72,000
Life
SEC Schedule, 12-16, Insurance Companies, Supplementary Insurance Information
Deferred policy acquisition costs	65,600	61,700	60,800
Future policy benefits, claims and claim expenses	1,279,700	1,245,400	1,201,600
Unearned premiums	1,500	1,300	1,200
Other policy claims and benefits payable	3,600	3,500	3,500
Premium revenue/ premium earned	108,400	120,200	119,600
Net investment income	83,100	69,800	72,000
Benefits, claims and settlement expenses	127,900	134,600	124,500
Amortization of deferred policy acquisition costs	7,400	7,400	7,800
Other operating expenses	$ 36,800	$ 35,300	$ 37,900