Reserves for Unpaid Losses and Loss Adjustment Expenses (Incurred and Paid Claims Development - Property) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) claim	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development	$ 60,900	$ 5,953
Incurred claims and claim adjustment expenses related to current year	301,265	250,075
Total incurred	362,165	256,028
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	192,335	232,345
Paid claims and allocated claim adjustment expenses related to current year	127,610	90,640
Total paid	319,945	322,985
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	347,751	305,531	$ 372,488
Property [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total incurred	191,214
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Total paid	179,725
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	11,489
Property [Member] | Loss Adjustment Expenses Recognized In 2010 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		9,496	9,700	$ 9,675	$ 9,654	$ 9,668	$ 9,656	$ 9,680	$ 9,836	$ 9,652
Incurred claims and claim adjustment expenses related to current year	$ 9,501
Cumulative number of reported claims | claim	1,316
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 9,501	9,496	9,496	9,498	9,479	9,474	9,479	9,522	9,632	$ 8,692
Property [Member] | Loss Adjustment Expenses Recognized In 2011 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		12,551	12,494	12,616	12,598	12,406	12,228	12,289	11,768
Incurred claims and claim adjustment expenses related to current year	$ 12,549
Cumulative number of reported claims | claim	1,512
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 12,549	12,551	12,550	12,541	12,492	12,370	12,343	12,354	$ 10,317
Property [Member] | Loss Adjustment Expenses Recognized In 2012 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		17,974	18,005	17,768	17,743	18,119	17,541	18,518
Incurred claims and claim adjustment expenses related to current year	$ 17,963
Cumulative number of reported claims | claim	1,629
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 17,963	17,974	17,978	17,693	17,666	17,743	17,679	$ 15,773
Property [Member] | Loss Adjustment Expenses Recognized In 2013 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		22,936	22,914	22,578	22,264	22,363	21,644
Incurred claims and claim adjustment expenses related to current year	$ 22,935
Cumulative number of reported claims | claim	1,893
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 22,935	22,936	22,826	22,197	21,864	21,452	$ 17,785
Property [Member] | Loss Adjustment Expenses Recognized In 2014 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		21,852	21,793	21,862	21,950	22,551
Incurred claims and claim adjustment expenses related to current year	21,876
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ (20)
Cumulative number of reported claims | claim	2,037
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 21,955	21,911	21,849	21,778	21,749	$ 19,586
Property [Member] | Loss Adjustment Expenses Recognized in 2015 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		20,091	20,014	19,919	20,256
Incurred claims and claim adjustment expenses related to current year	20,202
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 5
Cumulative number of reported claims | claim	1,993
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 19,953	20,134	19,928	19,500	$ 17,513
Property [Member] | Loss Adjustment Expenses Recognized in 2016 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		22,632	22,838	20,734
Incurred claims and claim adjustment expenses related to current year	22,789
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	2,029
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 22,789	22,613	22,500	$ 17,248
Property [Member] | Loss Adjustment Expenses Recognized in 2017 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		23,003	24,182
Incurred claims and claim adjustment expenses related to current year	24,490
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 10
Cumulative number of reported claims | claim	2,006
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 23,821	22,059	$ 18,703
Property [Member] | Loss Adjustment Expenses Recognized In 2018 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development		22,822
Incurred claims and claim adjustment expenses related to current year	18,694
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ (649)
Cumulative number of reported claims | claim	1,052
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 16,914	$ 10,923
Property [Member] | Loss Adjustment Expenses Recognized In 2019 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to current year	20,214
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 4,640
Cumulative number of reported claims | claim	997
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to current year	$ 11,344