Property and Casualty Unpaid Claims and Claim Expenses - Summary of Reinsurance Reserve Balances (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Beginning Gross reserves			$ 396,714
Claims and claim expense payments for claims occurring during:
Ending Gross reserves	$ 398,339		398,339
Benefits, claims and settlement expenses	152,692	$ 168,278	292,076	$ 311,840
Property and Casualty
Segment Reporting Information [Line Items]
Beginning Gross reserves	359,701	331,255	367,180	319,182
Less: reinsurance recoverables	78,328	62,917	89,725	57,409
Net reserves, beginning of year	281,373	268,338	277,455	261,773
Incurred claims and claim expenses:
Claims occurring in the current period	134,411	147,005	253,178	267,993
Decrease in estimated reserves for claims occurring in prior years	(2,000)	0	(4,000)	(300)
Total claims and claim expenses incurred	132,411	147,005	249,178	267,693
Claims and claim expense payments for claims occurring during:
Current period	83,755	80,403	129,469	127,451
Prior periods	39,512	45,006	106,647	112,081
Total claims and claim expense payments	123,267	125,409	236,116	239,532
Net reserves, end of year	290,517	289,934	290,517	289,934
Plus: reinsurance recoverables	77,345	62,883	77,345	62,883
Ending Gross reserves	367,862	352,817	367,862	352,817
Life and Annuity segments
Claims and claim expense payments for claims occurring during:
Net reserves, end of year	30,477	27,016	30,477	27,016
Benefits, claims and settlement expenses	$ 20,281	$ 21,273	$ 42,898	$ 44,147