Liability for Losses and Loss Expenses, Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance (Details) Claim in Thousands, $ in Thousands	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 ($)	Dec. 31, 2013 USD ($)
Personal Automobile [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 1,410,898
Personal Automobile [Member] | 2013 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	132,735	$ 132,787	$ 132,690	$ 132,853	$ 132,934	$ 132,604	$ 132,643	$ 131,594	$ 130,737	$ 124,965
Total IBNR plus expected development on reported claims	$ 51
Cumulative number of reported claims | Claim	66
Personal Automobile [Member] | 2014 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 127,108	126,977	126,861	126,734	126,779	126,200	124,210	124,806	124,426
Total IBNR plus expected development on reported claims	$ 65
Cumulative number of reported claims | Claim	71
Personal Automobile [Member] | 2015 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 141,965	142,010	142,073	142,408	142,493	139,181	139,333	137,569
Total IBNR plus expected development on reported claims	$ 135
Cumulative number of reported claims | Claim	70
Personal Automobile [Member] | 2016 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 156,227	156,436	156,935	157,943	157,516	153,937	150,216
Total IBNR plus expected development on reported claims	$ 522
Cumulative number of reported claims | Claim	73
Personal Automobile [Member] | 2017 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 173,032	173,730	174,784	175,939	127,728	166,690
Total IBNR plus expected development on reported claims	$ 901
Cumulative number of reported claims | Claim	79
Personal Automobile [Member] | 2018 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 179,732	180,787	181,558	183,358	186,580
Total IBNR plus expected development on reported claims	$ 1,695
Cumulative number of reported claims | Claim	81
Personal Automobile [Member] | 2019 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 154,805	156,300	157,689	161,056
Total IBNR plus expected development on reported claims	$ 2,559
Cumulative number of reported claims | Claim	68
Personal Automobile [Member] | 2020 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 100,339	103,585	111,483
Total IBNR plus expected development on reported claims	$ 3,324
Cumulative number of reported claims | Claim	43
Personal Automobile [Member] | 2021 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 118,752	119,364
Total IBNR plus expected development on reported claims	$ 6,432
Cumulative number of reported claims | Claim	47
Personal Automobile [Member] | 2022 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 126,203
Total IBNR plus expected development on reported claims	$ 19,934
Cumulative number of reported claims | Claim	48
Homeowners [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 678,947
Homeowners [Member] | 2013 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	51,021	51,053	51,064	51,008	50,971	50,988	50,874	51,122	51,121	50,887
Total IBNR plus expected development on reported claims	$ 0
Cumulative number of reported claims | Claim	13
Homeowners [Member] | 2014 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 57,353	57,371	57,367	57,402	57,288	57,332	57,680	58,378	56,916
Total IBNR plus expected development on reported claims	$ 0
Cumulative number of reported claims | Claim	17
Homeowners [Member] | 2015 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 63,036	63,043	62,993	63,099	63,071	63,053	63,925	63,359
Total IBNR plus expected development on reported claims	$ 10
Cumulative number of reported claims | Claim	14
Homeowners [Member] | 2016 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 63,472	63,409	63,279	63,355	63,735	64,064	62,443
Total IBNR plus expected development on reported claims	$ 35
Cumulative number of reported claims | Claim	12
Homeowners [Member] | 2017 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 78,815	79,065	79,247	79,305	79,911	79,283
Total IBNR plus expected development on reported claims	$ 62
Cumulative number of reported claims | Claim	17
Homeowners [Member] | 2018 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 82,058	82,566	82,905	83,385	81,965
Total IBNR plus expected development on reported claims	$ 230
Cumulative number of reported claims | Claim	18
Homeowners [Member] | 2019 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 72,168	73,234	73,554	73,294
Total IBNR plus expected development on reported claims	$ 457
Cumulative number of reported claims | Claim	16
Homeowners [Member] | 2020 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 61,595	62,718	61,633
Total IBNR plus expected development on reported claims	$ 835
Cumulative number of reported claims | Claim	14
Homeowners [Member] | 2021 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 66,996	67,677
Total IBNR plus expected development on reported claims	$ 1,455
Cumulative number of reported claims | Claim	11
Homeowners [Member] | 2022 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 82,433
Total IBNR plus expected development on reported claims	$ 7,556
Cumulative number of reported claims | Claim	9
Commercial Automobile [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 737,348
Commercial Automobile [Member] | 2013 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	36,133	36,165	36,181	36,569	36,435	36,404	35,240	34,751	33,749	32,902
Total IBNR plus expected development on reported claims	$ 27
Cumulative number of reported claims | Claim	8
Commercial Automobile [Member] | 2014 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 49,285	49,291	49,308	49,168	49,284	48,213	47,326	44,544	42,760
Total IBNR plus expected development on reported claims	$ 33
Cumulative number of reported claims | Claim	11
Commercial Automobile [Member] | 2015 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 53,477	53,793	54,619	54,517	54,259	51,412	48,323	46,526
Total IBNR plus expected development on reported claims	$ 74
Cumulative number of reported claims | Claim	12
Commercial Automobile [Member] | 2016 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 65,922	66,085	66,894	67,127	65,905	57,353	54,302
Total IBNR plus expected development on reported claims	$ 179
Cumulative number of reported claims | Claim	13
Commercial Automobile [Member] | 2017 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 64,631	65,310	67,249	67,697	67,927	61,484
Total IBNR plus expected development on reported claims	$ 205
Cumulative number of reported claims | Claim	14
Commercial Automobile [Member] | 2018 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 82,226	83,043	82,313	81,396	79,307
Total IBNR plus expected development on reported claims	$ 860
Cumulative number of reported claims | Claim	15
Commercial Automobile [Member] | 2019 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 86,140	90,290	91,245	88,864
Total IBNR plus expected development on reported claims	$ 3,066
Cumulative number of reported claims | Claim	16
Commercial Automobile [Member] | 2020 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 85,016	87,766	90,367
Total IBNR plus expected development on reported claims	$ 5,973
Cumulative number of reported claims | Claim	14
Commercial Automobile [Member] | 2021 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 99,231	109,824
Total IBNR plus expected development on reported claims	$ 16,504
Cumulative number of reported claims | Claim	14
Commercial Automobile [Member] | 2022 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 115,287
Total IBNR plus expected development on reported claims	$ 38,312
Cumulative number of reported claims | Claim	14
Commercial Multi-Peril [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 717,932
Commercial Multi-Peril [Member] | 2013 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	37,598	37,630	37,495	37,453	37,365	37,981	37,205	37,292	35,679	35,683
Total IBNR plus expected development on reported claims	$ 0
Cumulative number of reported claims | Claim	6
Commercial Multi-Peril [Member] | 2014 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 53,502	52,933	52,926	53,116	53,294	52,336	51,843	50,135	48,204
Total IBNR plus expected development on reported claims	$ 0
Cumulative number of reported claims | Claim	7
Commercial Multi-Peril [Member] | 2015 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 45,595	45,420	45,366	45,873	45,104	44,728	43,874	42,070
Total IBNR plus expected development on reported claims	$ 0
Cumulative number of reported claims | Claim	6
Commercial Multi-Peril [Member] | 2016 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 48,802	48,823	48,732	48,871	48,267	46,988	43,005
Total IBNR plus expected development on reported claims	$ 137
Cumulative number of reported claims | Claim	6
Commercial Multi-Peril [Member] | 2017 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 54,244	55,076	54,812	56,517	56,043	56,185
Total IBNR plus expected development on reported claims	$ 208
Cumulative number of reported claims | Claim	7
Commercial Multi-Peril [Member] | 2018 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 65,911	67,810	67,749	66,470	66,265
Total IBNR plus expected development on reported claims	$ 1,632
Cumulative number of reported claims | Claim	7
Commercial Multi-Peril [Member] | 2019 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 75,821	76,326	73,836	71,865
Total IBNR plus expected development on reported claims	$ 4,491
Cumulative number of reported claims | Claim	7
Commercial Multi-Peril [Member] | 2020 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 76,490	79,910	83,195
Total IBNR plus expected development on reported claims	$ 8,388
Cumulative number of reported claims | Claim	8
Commercial Multi-Peril [Member] | 2021 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 117,574	116,827
Total IBNR plus expected development on reported claims	$ 22,939
Cumulative number of reported claims | Claim	7
Commercial Multi-Peril [Member] | 2022 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 142,395
Total IBNR plus expected development on reported claims	$ 44,828
Cumulative number of reported claims | Claim	6
Workers Compensation [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 518,629
Workers Compensation [Member] | 2013 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	43,059	42,427	42,341	42,651	42,555	42,327	42,828	44,289	47,027	$ 46,325
Total IBNR plus expected development on reported claims	$ 1
Cumulative number of reported claims | Claim	6
Workers Compensation [Member] | 2014 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 47,794	47,620	47,849	47,693	47,540	48,537	49,288	51,553	$ 51,508
Total IBNR plus expected development on reported claims	$ 14
Cumulative number of reported claims | Claim	6
Workers Compensation [Member] | 2015 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 42,043	42,225	42,597	43,006	44,986	45,991	49,615	$ 53,332
Total IBNR plus expected development on reported claims	$ 240
Cumulative number of reported claims | Claim	5
Workers Compensation [Member] | 2016 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 43,484	43,559	44,098	44,969	47,883	49,802	$ 58,814
Total IBNR plus expected development on reported claims	$ 561
Cumulative number of reported claims | Claim	5
Workers Compensation [Member] | 2017 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 48,802	49,557	51,464	52,687	56,351	$ 60,450
Total IBNR plus expected development on reported claims	$ 1,105
Cumulative number of reported claims | Claim	5
Workers Compensation [Member] | 2018 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 47,007	47,912	52,514	55,291	$ 62,197
Total IBNR plus expected development on reported claims	$ 1,470
Cumulative number of reported claims | Claim	6
Workers Compensation [Member] | 2019 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 56,480	57,728	59,624	$ 60,998
Total IBNR plus expected development on reported claims	$ 1,897
Cumulative number of reported claims | Claim	6
Workers Compensation [Member] | 2020 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 57,384	57,850	$ 57,172
Total IBNR plus expected development on reported claims	$ 2,990
Cumulative number of reported claims | Claim	5
Workers Compensation [Member] | 2021 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 65,530	$ 67,035
Total IBNR plus expected development on reported claims	$ 6,505
Cumulative number of reported claims | Claim	6
Workers Compensation [Member] | 2022 [Member]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net [Abstract]
Incurred claims and allocated claim adjustment expenses, net of reinsurance	$ 67,046
Total IBNR plus expected development on reported claims	$ 21,062
Cumulative number of reported claims | Claim	6