Unpaid Claims and Claim Expenses - Summary of Reinsurance Reserve Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Unpaid Claims and Claims Adjustment Expense
Gross reserves, beginning of year	$ 438,800
Less: reinsurance recoverables	122,500
Claims and claim expense payments for claims occurring during:
Plus: reinsurance recoverables	119,600	$ 122,500
Gross reserves, end of year	425,900	438,800
Benefits, claims and settlement expenses	617,700	568,900	$ 585,100
Property & Casualty segment
Liability for Unpaid Claims and Claims Adjustment Expense
Gross reserves, beginning of year	372,200	387,000	367,200
Less: reinsurance recoverables	112,900	120,500	89,700
Net reserves, beginning of year	259,300	266,500	277,500
Incurred claims and claim expenses:
Claims occurring in the current year	455,100	441,200	483,100
Decrease in estimated reserves for claims occurring in prior years	(7,200)	(10,200)	(7,500)
Total claims and claim expenses incurred	447,900	431,000	475,600
Claims and claim expense payments for claims occurring during:
Current year	307,100	291,400	329,500
Prior years	148,000	146,800	157,100
Total claims and claim expense payments	455,100	438,200	486,600
Net reserves, end of year	252,100	259,300	266,500
Plus: reinsurance recoverables	110,300	112,900	120,500
Gross reserves, end of year	362,400	372,200	387,000
Life and Annuity segments
Liability for Unpaid Claims and Claims Adjustment Expense
Net reserves, beginning of year	66,600	55,900
Claims and claim expense payments for claims occurring during:
Net reserves, end of year	63,500	66,600	55,900
Benefits, claims and settlement expenses	$ 169,800	$ 137,900	$ 109,500