Reserves for Losses and Loss Adjustment Expenses (Incurred and Paid Claims Development - Commercial Accounts) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) claim	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development	$ 6,040	$ 58,288
Incurred claims and claim adjustment expenses related to current year	269,204	326,919
Total incurred	275,244	406,907
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	177,571	185,407
Paid claims and allocated claim adjustment expenses related to current year	101,475	113,312
Total paid	279,046	320,419
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	428,766	432,568	$ 346,080
Loss Adjustment Expenses Recognized In 2012 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years										$ 1,181
Commercial Accounts business unit [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total incurred	416,667
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Total paid	357,772
All outstanding liabilities before 2012, net of reinsurance	1,616
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	60,511
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2012 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		39,462	38,669	$ 38,669	$ 40,350	$ 41,451	$ 42,632	$ 44,625	$ 48,085	47,194
Incurred claims and claim adjustment expenses related to current year	39,626
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 208
Cumulative number of reported claims | claim	2,712
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 39,108	38,518	38,211	38,044	37,808	35,943	34,597	32,378	30,096	$ 22,264
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2013 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		40,141	40,211	39,567	42,822	43,917	46,990	47,385	46,413
Incurred claims and claim adjustment expenses related to current year	40,562
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 178
Cumulative number of reported claims | claim	2,809
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 40,210	39,560	39,329	38,892	37,947	36,225	33,927	29,586	$ 19,386
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2014 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		42,503	42,463	43,673	43,806	43,806	46,470	46,280
Incurred claims and claim adjustment expenses related to current year	42,645
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 201
Cumulative number of reported claims | claim	2,742
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 41,863	41,658	41,162	39,185	36,775	33,544	31,150	$ 21,322
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized in 2015 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		39,206	39,287	38,385	41,429	42,580	40,966
Incurred claims and claim adjustment expenses related to current year	38,677
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 512
Cumulative number of reported claims | claim	2,579
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 37,886	37,135	35,611	35,238	30,974	28,501	$ 16,557
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized in 2016 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		45,267	43,111	41,983	43,449	43,327
Incurred claims and claim adjustment expenses related to current year	43,883
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 795
Cumulative number of reported claims | claim	2,548
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 42,819	40,828	39,417	35,035	29,456	$ 19,776
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized in 2017 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		44,732	43,579	42,704	40,943
Incurred claims and claim adjustment expenses related to current year	45,815
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 1,259
Cumulative number of reported claims | claim	2,745
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 42,707	41,631	36,650	28,813	$ 16,644
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2018 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		44,590	41,290	42,898
Incurred claims and claim adjustment expenses related to current year	47,007
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 2,920
Cumulative number of reported claims | claim	2,606
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 40,163	33,546	29,381	$ 19,233
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2019 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		34,616	37,984
Incurred claims and claim adjustment expenses related to current year	36,044
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 2,867
Cumulative number of reported claims | claim	2,754
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 30,407	26,233	$ 17,490
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2020 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable (favorable) net prior year development		40,356
Incurred claims and claim adjustment expenses related to current year	35,879
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 8,597
Cumulative number of reported claims | claim	2,793
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 23,914	$ 13,942
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2021 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to current year	46,529
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 21,462
Cumulative number of reported claims | claim	2,539
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to current year	$ 18,695