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Loss And Loss Adjustment Expense Reserves - Incurred and Paid Claims (Details) number_of_claims in Thousands, $ in Thousands	Dec. 31, 2022 USD ($) number_of_claims	Dec. 31, 2021 USD ($)	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 ($)	Dec. 31, 2013 USD ($)
Claims Development [Line Items]
Net outstanding liabilities	$ 2,420,897
Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	17,473,673
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	15,567,485
All outstanding liabilities before 2013, net of reinsurance	(1,048)
Net outstanding liabilities	1,905,140
Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	3,356,128
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	3,016,971
All outstanding liabilities before 2013, net of reinsurance	1,152
Net outstanding liabilities	340,309
2013 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,468,976	$ 1,468,679	$ 1,468,747	$ 1,468,237	$ 1,468,294	$ 1,464,071	$ 1,458,421	$ 1,447,881	$ 1,431,058	$ 1,448,567
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 805
Cumulative Number of Reported Claims | number_of_claims	185
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,467,838	1,467,332	1,466,356	1,464,277	1,460,352	1,447,004	1,413,999	1,340,724	1,217,906	974,445
2013 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	187,465	187,627	187,683	187,147	188,014	187,165	186,795	188,026	188,915	191,903
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 95
Cumulative Number of Reported Claims | number_of_claims	23
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 187,222	187,141	186,816	186,494	186,132	185,168	183,860	180,858	174,295	$ 133,528
2014 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,502,161	1,501,850	1,501,713	1,501,075	1,498,504	1,486,322	1,473,545	1,454,366	1,467,175
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 57
Cumulative Number of Reported Claims | number_of_claims	180
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,501,483	1,500,243	1,496,814	1,490,366	1,476,944	1,432,472	1,358,472	1,231,413	967,481
2014 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	209,071	209,622	208,743	208,003	204,986	202,513	203,218	202,621	199,298
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 128
Cumulative Number of Reported Claims | number_of_claims	25
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 208,737	207,801	207,524	203,333	202,193	198,758	194,605	186,996	$ 139,615
2015 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,654,843	1,653,878	1,649,170	1,645,950	1,634,435	1,610,839	1,588,443	1,551,105
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 1,078
Cumulative Number of Reported Claims | number_of_claims	170
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,651,465	1,643,443	1,634,780	1,614,188	1,560,480	1,466,368	1,336,223	1,040,253
2015 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	237,872	240,927	239,941	238,652	236,855	233,501	234,881	234,800
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 393
Cumulative Number of Reported Claims | number_of_claims	24
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 236,983	236,143	235,971	234,683	230,480	224,178	213,994	$ 163,196
2016 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,743,417	1,740,807	1,732,410	1,731,997	1,713,696	1,669,642	1,672,853
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 2,483
Cumulative Number of Reported Claims | number_of_claims	155
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,736,697	1,722,293	1,699,069	1,656,192	1,554,217	1,395,199	1,094,006
2016 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	259,722	259,984	260,496	259,708	259,497	259,489	250,691
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 435
Cumulative Number of Reported Claims | number_of_claims	24
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 259,045	258,477	256,642	253,919	245,878	234,215	$ 173,537
2017 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,755,702	1,748,289	1,733,425	1,741,825	1,727,277	1,703,857
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 11,421
Cumulative Number of Reported Claims | number_of_claims	149
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,733,196	1,701,298	1,648,328	1,561,850	1,399,202	1,076,079
2017 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	291,360	289,294	289,869	288,322	295,163	309,491
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 92
Cumulative Number of Reported Claims | number_of_claims	30
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 290,291	286,531	283,311	278,341	269,254	$ 217,900
2018 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,807,297	1,806,240	1,785,071	1,773,502	1,781,817
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 15,370
Cumulative Number of Reported Claims | number_of_claims	147
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,757,923	1,697,228	1,588,049	1,417,637	1,082,127
2018 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	306,347	305,292	310,695	308,361	311,798
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 1,192
Cumulative Number of Reported Claims | number_of_claims	25
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 300,742	294,099	286,658	271,534	$ 213,038
2019 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,954,151	1,959,262	1,911,268	1,916,269
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 42,928
Cumulative Number of Reported Claims | number_of_claims	148
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,828,410	1,698,121	1,494,342	1,134,859
2019 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	360,609	361,421	366,139	359,643
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 4,888
Cumulative Number of Reported Claims | number_of_claims	30
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 350,288	340,237	324,953	$ 240,240
2020 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,452,343	1,448,083	1,514,551
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 76,899
Cumulative Number of Reported Claims | number_of_claims	90
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,242,000	1,089,096	825,398
2020 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	413,882	411,404	420,257
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 7,838
Cumulative Number of Reported Claims | number_of_claims	29
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 386,297	365,910	$ 271,208
2021 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	1,879,751	1,811,064
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 206,875
Cumulative Number of Reported Claims | number_of_claims	104
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,410,748	992,705
2021 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	511,311	510,724
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 22,449
Cumulative Number of Reported Claims | number_of_claims	31
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 458,124	$ 316,314
2022 | Property insurance product line, automobile
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	2,255,032
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 642,129
Cumulative Number of Reported Claims | number_of_claims	109
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 1,237,725
2022 | Property insurance product line, homeowners'
Claims Development [Line Items]
Incurred Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	578,489
Total of Incurred But Not Reported Liabilities Plus Expected Development on Reported Claims	$ 135,547
Cumulative Number of Reported Claims | number_of_claims	27
Cumulative Paid Losses and Allocated Loss Adjustment Expenses, Net of Reinsurance	$ 339,242

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Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.

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Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts for accident years not separately presented in claim development information. Excludes unallocated claim adjustment expense.

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