Reserves for Losses and Loss Adjustment Expenses (Incurred and Paid Claims Development - Commercial Accounts) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($) claim	Dec. 31, 2021 USD ($)	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 ($)	Dec. 31, 2013 USD ($)
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total unfavorable net prior year development	$ 112,300	$ 6,000
Incurred claims and claim adjustment expenses related to current year	117,644	151,603
Total incurred	323,499	275,244
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Total paid	292,089	279,046
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	460,176	428,766	$ 432,568
Commercial Accounts business unit [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total incurred	423,246
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Total paid	357,984
All outstanding liabilities before 2012, net of reinsurance	1,446
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	66,708
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 net prior year development		40,562	40,141	$ 40,211	$ 40,350	$ 41,451	$ 42,632	$ 44,625	$ 48,085	$ 47,194
Incurred claims and claim adjustment expenses related to current year	40,795
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 307
Cumulative number of reported claims | claim	2,812
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 40,278	40,210	39,560	39,329	37,808	35,943	34,597	32,378	30,096	$ 22,264
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 net prior year development		42,645	42,503	42,463	42,822	43,917	46,990	47,385	46,413
Incurred claims and claim adjustment expenses related to current year	42,870
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 474
Cumulative number of reported claims | claim	2,744
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 42,030	41,863	41,658	41,162	37,947	36,225	33,927	29,586	$ 19,386
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 net prior year development		38,677	39,206	39,287	43,806	43,806	46,470	46,280
Incurred claims and claim adjustment expenses related to current year	39,417
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 962
Cumulative number of reported claims | claim	2,582
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 38,303	37,886	37,135	35,611	36,775	33,544	31,150	$ 21,322
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 net prior year development		43,883	45,267	43,111	41,429	42,580	40,966
Incurred claims and claim adjustment expenses related to current year	44,566
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 1,224
Cumulative number of reported claims | claim	2,550
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 43,101	42,819	40,828	39,417	30,974	28,501	$ 16,557
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 net prior year development		45,815	44,732	43,579	43,449	43,327
Incurred claims and claim adjustment expenses related to current year	46,617
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 2,147
Cumulative number of reported claims | claim	2,751
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 44,381	42,707	41,631	36,650	29,456	$ 19,776
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 net prior year development		47,007	44,590	41,290	40,943
Incurred claims and claim adjustment expenses related to current year	46,256
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 3,143
Cumulative number of reported claims | claim	2,619
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 42,794	40,163	33,546	29,381	$ 16,664
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 net prior year development		36,044	34,616	37,984
Incurred claims and claim adjustment expenses related to current year	39,298
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 2,517
Cumulative number of reported claims | claim	2,778
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 33,914	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 net prior year development		35,879	40,356
Incurred claims and claim adjustment expenses related to current year	34,197
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 2,943
Cumulative number of reported claims | claim	2,836
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 26,881	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]
Total unfavorable net prior year development		46,529
Incurred claims and claim adjustment expenses related to current year	43,347
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 9,266
Cumulative number of reported claims | claim	2,862
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 29,230	$ 18,695
Commercial Accounts business unit [Member] | Loss Adjustment Expenses Recognized In 2022 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to current year	45,883
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 18,674
Cumulative number of reported claims | claim	2,149
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to current year	$ 17,072