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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Beginning Gross reserves			$ 329,888
Claims and claim expense payments for claims occurring during:
Ending Gross reserves	$ 352,513		352,513
Benefits, claims and settlement expenses	165,879	$ 148,408	309,975	$ 267,921
Property and Casualty segment
Segment Reporting Information [Line Items]
Beginning Gross reserves	316,173	319,276	307,757	301,569
Less: reinsurance recoverables	61,804	60,429	61,199	50,332
Net reserves, beginning of year	254,369	258,847	246,558	251,237
Incurred claims and claim expenses:
Claims occurring in the current period	148,348	131,355	271,552	234,561
Decrease in estimated reserves for claims occurring in prior years	(600)	(1,600)	(1,600)	(3,600)
Total claims and claim expenses incurred	147,748	129,755	269,952	230,961
Claims and claim expense payments for claims occurring during:
Current period	95,645	89,549	148,025	128,630
Prior periods	35,538	38,591	97,551	93,106
Total claims and claim expense payments	131,183	128,140	245,576	221,736
Net reserves, end of year	270,934	260,462	270,934	260,462
Plus: reinsurance recoverables	58,897	60,499	58,897	60,499
Ending Gross reserves	329,831	320,961	329,831	320,961
Life and Annuity segments
Claims and claim expense payments for claims occurring during:
Net reserves, end of year	22,682	23,783	22,682	23,783
Benefits, claims and settlement expenses	$ 18,131	$ 18,653	$ 40,023	$ 36,960