Property and Casualty Unpaid Claims and Claim Expenses - Summary of Reinsurance Reserve Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Gross reserves, beginning of year	$ 347,749
Less: reinsurance recoverables	68,446
Claims and claim expense payments for claims occurring during:
Plus: reinsurance recoverables	99,510	$ 68,446
Gross reserves, end of year	396,714	347,749
Benefits, claims and settlement expenses, Net Amount	637,560	582,306	$ 541,004
Property and Casualty segment
Segment Reporting Information [Line Items]
Gross reserves, beginning of year	319,182	307,757	301,569
Less: reinsurance recoverables	57,409	61,199	50,332
Net reserves, beginning of year	261,773	246,558	251,237
Incurred claims and claim expenses:
Claims occurring in the current year	547,959	498,989	471,099
Decrease in estimated reserves for claims occurring in prior years	(300)	(2,700)	(7,000)
Total claims and claim expenses incurred	547,659	496,289	464,099
Claims and claim expense payments for claims occurring during:
Current year	369,194	333,385	323,025
Prior years	162,783	147,689	145,753
Total claims and claim expense payments	531,977	481,074	468,778
Net reserves, end of year	277,455	261,773	246,558
Plus: reinsurance recoverables	89,725	57,409	61,199
Gross reserves, end of year	367,180	319,182	307,757
Life and Annuity segments
Segment Reporting Information [Line Items]
Net reserves, beginning of year	28,567	22,131
Claims and claim expense payments for claims occurring during:
Net reserves, end of year	29,534	28,567	22,131
Benefits, claims and settlement expenses, Net Amount	$ 89,901	$ 86,017	$ 76,905