Reserve for Losses and Loss Adjustment Expenses - Claim Development (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) claim	Dec. 31, 2019 USD ($)	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 ($)	Dec. 31, 2011 USD ($)
Claims Development [Line Items]
Liabilities for losses and loss adjustment expenses, net of reinsurance	$ 1,838,703
Healthcare Professional Liability claims-made
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,948,871
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,758,491
All outstanding liabilities before 2011, net of reinsurance	16,866
Liabilities for losses and loss adjustment expenses, net of reinsurance	1,207,246
Healthcare Professional Liability claims-made | 2011
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	251,440	$ 253,163	$ 254,329	$ 264,777	$ 278,258	$ 289,400	$ 305,540	$ 331,884	$ 344,808	$ 348,916
Incurred but Not Reported Liabilities (IBNR)	$ (1,522)
Cumulative Number of Reported Claims | claim	3,530
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 242,034	237,605	233,103	224,982	214,502	198,112	177,089	133,004	71,208	14,417
Healthcare Professional Liability claims-made | 2012
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	264,932	266,629	271,110	279,589	291,075	306,956	319,613	324,418	341,289
Incurred but Not Reported Liabilities (IBNR)	$ (180)
Cumulative Number of Reported Claims | claim	3,699
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 256,802	250,806	244,512	231,652	215,220	190,997	145,488	73,571	15,382
Healthcare Professional Liability claims-made | 2013
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	249,477	248,594	258,251	272,364	287,140	296,550	304,209	315,346
Incurred but Not Reported Liabilities (IBNR)	$ (2,266)
Cumulative Number of Reported Claims | claim	3,770
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 231,930	220,402	213,879	197,265	171,681	127,496	69,657	16,938
Healthcare Professional Liability claims-made | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	237,091	244,607	256,968	267,442	280,043	289,397	290,020
Incurred but Not Reported Liabilities (IBNR)	$ (3,596)
Cumulative Number of Reported Claims | claim	3,316
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 210,534	200,392	186,239	154,236	116,791	59,485	16,764
Healthcare Professional Liability claims-made | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	256,082	256,785	270,814	271,138	269,980	276,492
Incurred but Not Reported Liabilities (IBNR)	$ (8,109)
Cumulative Number of Reported Claims | claim	3,267
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 218,066	195,047	161,896	111,741	55,731	9,172
Healthcare Professional Liability claims-made | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	287,142	293,515	287,551	274,643	271,765
Incurred but Not Reported Liabilities (IBNR)	$ (5,250)
Cumulative Number of Reported Claims | claim	3,475
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 203,390	164,811	109,756	51,869	9,027
Healthcare Professional Liability claims-made | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	325,919	331,304	295,883	283,746
Incurred but Not Reported Liabilities (IBNR)	$ (11,542)
Cumulative Number of Reported Claims | claim	3,719
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 173,183	134,787	63,171	16,309
Healthcare Professional Liability claims-made | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	376,111	377,908	320,772
Incurred but Not Reported Liabilities (IBNR)	$ (26,964)
Cumulative Number of Reported Claims | claim	4,150
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 141,609	79,291	14,051
Healthcare Professional Liability claims-made | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	374,525	377,242
Incurred but Not Reported Liabilities (IBNR)	$ 69,993
Cumulative Number of Reported Claims | claim	3,574
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 66,843	17,838
Healthcare Professional Liability claims-made | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	326,152
Incurred but Not Reported Liabilities (IBNR)	$ 203,515
Cumulative Number of Reported Claims | claim	2,475
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 14,100
Healthcare Professional Liability occurrence
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	352,191
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	142,386
All outstanding liabilities before 2011, net of reinsurance	6,115
Liabilities for losses and loss adjustment expenses, net of reinsurance	215,920
Healthcare Professional Liability occurrence | 2011
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	27,287	27,533	29,784	32,343	35,004	37,150	39,917	41,453	44,956	45,882
Incurred but Not Reported Liabilities (IBNR)	$ (254)
Cumulative Number of Reported Claims | claim	344
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 25,111	24,933	24,539	23,194	21,416	19,197	16,544	8,059	2,803	291
Healthcare Professional Liability occurrence | 2012
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	26,533	25,705	29,857	32,691	34,774	40,692	44,848	46,513	45,703
Incurred but Not Reported Liabilities (IBNR)	$ 143
Cumulative Number of Reported Claims | claim	400
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 24,138	23,600	23,095	21,435	19,275	12,212	7,705	2,430	363
Healthcare Professional Liability occurrence | 2013
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	24,782	24,857	26,919	30,906	34,393	35,624	36,602	32,746
Incurred but Not Reported Liabilities (IBNR)	$ 74
Cumulative Number of Reported Claims | claim	360
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 21,954	21,241	18,949	16,787	14,753	7,826	3,170	369
Healthcare Professional Liability occurrence | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	22,048	22,243	25,885	29,869	32,143	29,918	30,420
Incurred but Not Reported Liabilities (IBNR)	$ 362
Cumulative Number of Reported Claims | claim	347
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 17,708	17,024	14,604	10,519	7,460	2,260	394
Healthcare Professional Liability occurrence | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	33,262	36,468	40,960	37,346	35,347	35,648
Incurred but Not Reported Liabilities (IBNR)	$ (1,059)
Cumulative Number of Reported Claims | claim	361
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 22,455	15,462	11,626	4,854	786	(350)
Healthcare Professional Liability occurrence | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	29,426	25,019	27,240	28,790	29,609
Incurred but Not Reported Liabilities (IBNR)	$ 2,174
Cumulative Number of Reported Claims | claim	373
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 17,918	10,576	2,883	(195)	(182)
Healthcare Professional Liability occurrence | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	21,498	21,148	23,760	24,571
Incurred but Not Reported Liabilities (IBNR)	$ 5,199
Cumulative Number of Reported Claims | claim	415
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 1,313	(2,765)	(5,858)	(6,809)
Healthcare Professional Liability occurrence | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	40,304	41,555	38,420
Incurred but Not Reported Liabilities (IBNR)	$ 11,413
Cumulative Number of Reported Claims | claim	389
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 8,562	2,098	65
Healthcare Professional Liability occurrence | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	34,093	35,420
Incurred but Not Reported Liabilities (IBNR)	$ 20,945
Cumulative Number of Reported Claims | claim	339
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,167	439
Healthcare Professional Liability occurrence | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	92,958
Incurred but Not Reported Liabilities (IBNR)	$ 90,916
Cumulative Number of Reported Claims | claim	130
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 60
Medical Technology Liability claims-made
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	63,522
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	32,666
All outstanding liabilities before 2011, net of reinsurance	351
Liabilities for losses and loss adjustment expenses, net of reinsurance	31,207
Medical Technology Liability claims-made | 2011
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	7,725	7,944	8,202	12,358	12,487	13,794	15,836	19,166	20,930	17,249
Incurred but Not Reported Liabilities (IBNR)	$ 60
Cumulative Number of Reported Claims | claim	522
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 7,665	7,665	7,664	7,799	7,240	7,376	5,062	3,846	2,034	118
Medical Technology Liability claims-made | 2012
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,868	3,889	5,051	4,797	5,824	7,441	8,906	9,989	11,162
Incurred but Not Reported Liabilities (IBNR)	$ 51
Cumulative Number of Reported Claims | claim	223
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,817	3,817	3,800	3,676	3,366	3,247	2,805	1,520	568
Medical Technology Liability claims-made | 2013
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	3,305	3,504	3,566	4,697	7,226	9,536	9,955	9,807
Incurred but Not Reported Liabilities (IBNR)	$ 201
Cumulative Number of Reported Claims | claim	218
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,102	3,102	3,102	3,092	2,599	1,967	1,029	102
Medical Technology Liability claims-made | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,888	6,194	7,679	8,984	9,012	10,306	9,989
Incurred but Not Reported Liabilities (IBNR)	$ 396
Cumulative Number of Reported Claims | claim	272
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 4,074	3,776	3,724	3,046	2,564	1,527	388
Medical Technology Liability claims-made | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,664	5,081	5,929	7,193	8,757	9,376
Incurred but Not Reported Liabilities (IBNR)	$ 1,194
Cumulative Number of Reported Claims | claim	156
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,911	2,567	2,097	1,625	440	25
Medical Technology Liability claims-made | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	6,241	6,422	7,413	8,467	9,200
Incurred but Not Reported Liabilities (IBNR)	$ 1,374
Cumulative Number of Reported Claims | claim	182
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 4,295	2,959	2,365	1,690	53
Medical Technology Liability claims-made | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,919	8,306	10,143	11,049
Incurred but Not Reported Liabilities (IBNR)	$ 2,017
Cumulative Number of Reported Claims | claim	99
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,360	2,017	1,681	56
Medical Technology Liability claims-made | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	7,506	8,108	10,141
Incurred but Not Reported Liabilities (IBNR)	$ 4,595
Cumulative Number of Reported Claims | claim	218
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 1,850	191	6
Medical Technology Liability claims-made | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	8,324	10,072
Incurred but Not Reported Liabilities (IBNR)	$ 4,830
Cumulative Number of Reported Claims | claim	354
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 2,552	584
Medical Technology Liability claims-made | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	11,082
Incurred but Not Reported Liabilities (IBNR)	$ 10,497
Cumulative Number of Reported Claims | claim	154
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 40
Workers' Compensation Insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	948,129
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	799,745
All outstanding liabilities before 2011, net of reinsurance	3,425
Liabilities for losses and loss adjustment expenses, net of reinsurance	151,809
Workers' Compensation Insurance | 2011
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	72,445	72,445	72,495	72,495	72,495	72,420	72,280	71,521	65,783	65,665
Incurred but Not Reported Liabilities (IBNR)	$ 21
Cumulative Number of Reported Claims | claim	15,245
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 72,013	71,927	71,856	71,662	70,934	70,146	67,945	62,307	50,900	21,993
Workers' Compensation Insurance | 2012
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	75,076	75,076	75,076	75,576	75,836	76,357	75,848	76,551	80,285
Incurred but Not Reported Liabilities (IBNR)	$ 672
Cumulative Number of Reported Claims | claim	16,204
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 73,851	73,768	73,676	73,662	72,766	70,558	65,908	56,122	27,448
Workers' Compensation Insurance | 2013
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	89,560	89,760	87,260	87,260	88,010	86,928	85,935	86,973
Incurred but Not Reported Liabilities (IBNR)	$ 983
Cumulative Number of Reported Claims | claim	16,429
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 87,772	87,466	86,783	85,689	82,369	76,813	63,825	30,554
Workers' Compensation Insurance | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	91,329	93,029	93,029	93,029	93,029	93,529	93,019
Incurred but Not Reported Liabilities (IBNR)	$ 1,594
Cumulative Number of Reported Claims | claim	16,210
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 88,487	87,998	87,314	85,022	77,631	65,922	30,368
Workers' Compensation Insurance | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	93,054	96,354	97,654	98,454	100,454	100,101
Incurred but Not Reported Liabilities (IBNR)	$ 2,248
Cumulative Number of Reported Claims | claim	16,550
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 87,884	86,528	83,483	78,947	65,070	32,078
Workers' Compensation Insurance | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	82,799	84,799	92,148	97,348	101,348
Incurred but Not Reported Liabilities (IBNR)	$ 2,149
Cumulative Number of Reported Claims | claim	15,978
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 76,954	74,886	69,237	58,192	28,377
Workers' Compensation Insurance | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	97,874	99,874	99,874	99,874
Incurred but Not Reported Liabilities (IBNR)	$ 4,581
Cumulative Number of Reported Claims | claim	16,083
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 87,129	82,289	70,333	31,586
Workers' Compensation Insurance | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	120,095	118,095	118,095
Incurred but Not Reported Liabilities (IBNR)	$ 2,054
Cumulative Number of Reported Claims | claim	18,009
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 104,216	86,063	41,619
Workers' Compensation Insurance | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	119,752	119,752
Incurred but Not Reported Liabilities (IBNR)	$ 9,768
Cumulative Number of Reported Claims | claim	17,517
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 88,008	40,994
Workers' Compensation Insurance | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	106,145
Incurred but Not Reported Liabilities (IBNR)	$ 35,455
Cumulative Number of Reported Claims | claim	13,994
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 33,431
Segregated Portfolio Cell Reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	300,735
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	247,631
All outstanding liabilities before 2011, net of reinsurance	600
Liabilities for losses and loss adjustment expenses, net of reinsurance	53,704
Segregated Portfolio Cell Reinsurance | 2011
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	18,212	18,522	18,606	18,666	18,725	18,644	19,282	19,629	19,360	18,790
Incurred but Not Reported Liabilities (IBNR)	$ 27
Cumulative Number of Reported Claims | claim	3,154
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 18,185	18,185	18,185	18,176	18,177	18,054	17,869	17,197	14,045	$ 5,940
Segregated Portfolio Cell Reinsurance | 2012
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	19,602	19,727	19,799	19,864	19,972	20,028	21,048	21,513	22,940
Incurred but Not Reported Liabilities (IBNR)	$ 152
Cumulative Number of Reported Claims | claim	3,454
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 19,340	19,311	19,328	19,402	19,208	18,474	17,728	14,740	$ 7,808
Segregated Portfolio Cell Reinsurance | 2013
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	25,546	25,938	26,033	26,260	26,619	26,758	25,310	23,809
Incurred but Not Reported Liabilities (IBNR)	$ 104
Cumulative Number of Reported Claims | claim	3,723
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 25,442	25,440	25,489	25,366	25,209	24,268	19,054	$ 8,131
Segregated Portfolio Cell Reinsurance | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	27,482	27,919	28,281	28,373	29,000	28,423	28,248
Incurred but Not Reported Liabilities (IBNR)	$ 188
Cumulative Number of Reported Claims | claim	4,433
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 27,110	27,083	26,959	26,810	26,173	21,880	9,933
Segregated Portfolio Cell Reinsurance | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	26,121	26,720	27,548	28,746	32,519	36,423
Incurred but Not Reported Liabilities (IBNR)	$ 372
Cumulative Number of Reported Claims | claim	4,949
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 25,125	25,033	24,781	23,977	21,706	11,257
Segregated Portfolio Cell Reinsurance | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	28,437	29,424	30,998	34,055	37,601
Incurred but Not Reported Liabilities (IBNR)	$ 515
Cumulative Number of Reported Claims | claim	5,327
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 27,211	27,162	26,285	23,003	10,980
Segregated Portfolio Cell Reinsurance | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	32,879	34,246	38,594	42,725
Incurred but Not Reported Liabilities (IBNR)	$ 775
Cumulative Number of Reported Claims | claim	5,706
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 31,140	28,853	24,791	12,404
Segregated Portfolio Cell Reinsurance | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	40,017	41,283	43,654
Incurred but Not Reported Liabilities (IBNR)	$ 2,979
Cumulative Number of Reported Claims | claim	6,373
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 33,236	27,501	12,517
Segregated Portfolio Cell Reinsurance | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	42,345	48,505
Incurred but Not Reported Liabilities (IBNR)	$ 6,461
Cumulative Number of Reported Claims | claim	6,081
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 29,604	15,100
Segregated Portfolio Cell Reinsurance | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	40,094
Incurred but Not Reported Liabilities (IBNR)	$ 16,479
Cumulative Number of Reported Claims | claim	5,587
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 11,238
Syndicate 1729 casualty
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	109,480
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	57,905
All outstanding liabilities before 2011, net of reinsurance	0
Liabilities for losses and loss adjustment expenses, net of reinsurance	51,575
Syndicate 1729 casualty | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,435	5,432	5,472	5,547	5,610	5,812	6,110
Incurred but Not Reported Liabilities (IBNR)	333
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	4,852	4,580	4,320	4,214	4,092	474	20
Syndicate 1729 casualty | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	14,031	14,181	14,232	14,398	14,510	14,810
Incurred but Not Reported Liabilities (IBNR)	1,156
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	12,104	11,654	10,947	10,313	6,307	724
Syndicate 1729 casualty | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	18,358	19,344	19,552	19,669	19,535
Incurred but Not Reported Liabilities (IBNR)	2,511
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	14,436	13,596	12,869	8,441	2,495
Syndicate 1729 casualty | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	23,130	21,207	21,824	22,069
Incurred but Not Reported Liabilities (IBNR)	4,502
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	14,990	12,871	8,301	2,611
Syndicate 1729 casualty | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	16,569	18,120	18,688
Incurred but Not Reported Liabilities (IBNR)	7,181
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	6,710	4,905	1,852
Syndicate 1729 casualty | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	16,699	15,990
Incurred but Not Reported Liabilities (IBNR)	11,190
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,831	1,124
Syndicate 1729 casualty | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	15,258
Incurred but Not Reported Liabilities (IBNR)	12,714
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,982
Syndicate 1729 property insurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	98,821
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	77,470
All outstanding liabilities before 2011, net of reinsurance	0
Liabilities for losses and loss adjustment expenses, net of reinsurance	21,351
Syndicate 1729 property insurance | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	882	831	866	864	888	1,089	890
Incurred but Not Reported Liabilities (IBNR)	$ 8
Cumulative Number of Reported Claims | claim	68
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 860	860	857	854	836	1,005	267
Syndicate 1729 property insurance | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	5,215	5,886	6,159	6,194	5,917	5,519
Incurred but Not Reported Liabilities (IBNR)	$ 61
Cumulative Number of Reported Claims | claim	538
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 5,117	5,018	4,869	4,808	4,022	3,165
Syndicate 1729 property insurance | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	12,835	12,475	12,823	12,984	11,896
Incurred but Not Reported Liabilities (IBNR)	$ 152
Cumulative Number of Reported Claims | claim	1,467
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 12,623	12,400	12,343	10,939	7,751
Syndicate 1729 property insurance | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	19,866	19,976	17,634	15,018
Incurred but Not Reported Liabilities (IBNR)	$ 275
Cumulative Number of Reported Claims | claim	2,686
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 20,097	19,404	16,439	8,221
Syndicate 1729 property insurance | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	21,903	21,888	20,636
Incurred but Not Reported Liabilities (IBNR)	$ 307
Cumulative Number of Reported Claims | claim	3,612
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 19,769	17,248	9,918
Syndicate 1729 property insurance | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	19,664	18,010
Incurred but Not Reported Liabilities (IBNR)	$ 983
Cumulative Number of Reported Claims | claim	4,122
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 11,643	5,575
Syndicate 1729 property insurance | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	18,456
Incurred but Not Reported Liabilities (IBNR)	$ 3,411
Cumulative Number of Reported Claims | claim	2,848
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 7,361
Syndicate 1729 property reinsurance
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	38,632
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	27,362
All outstanding liabilities before 2011, net of reinsurance	0
Liabilities for losses and loss adjustment expenses, net of reinsurance	11,270
Syndicate 1729 property reinsurance | 2014
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,112	1,120	1,125	989	989	929	831
Incurred but Not Reported Liabilities (IBNR)	0
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,112	1,120	1,125	984	984	917	$ 79
Syndicate 1729 property reinsurance | 2015
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,455	2,377	2,328	2,275	2,825	2,788
Incurred but Not Reported Liabilities (IBNR)	59
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,303	2,267	2,234	1,996	1,804	$ 1,313
Syndicate 1729 property reinsurance | 2016
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,498	2,832	3,368	4,050	4,497
Incurred but Not Reported Liabilities (IBNR)	98
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,215	2,192	2,136	1,667	$ 613
Syndicate 1729 property reinsurance | 2017
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	7,947	6,868	7,832	6,861
Incurred but Not Reported Liabilities (IBNR)	44
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	7,563	8,947	7,300	$ 4,147
Syndicate 1729 property reinsurance | 2018
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	2,887	6,398	8,840
Incurred but Not Reported Liabilities (IBNR)	590
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	1,663	1,644	$ 547
Syndicate 1729 property reinsurance | 2019
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	13,333	10,977
Incurred but Not Reported Liabilities (IBNR)	1,704
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	8,575	$ 4,974
Syndicate 1729 property reinsurance | 2020
Claims Development [Line Items]
Incurred Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	8,400
Incurred but Not Reported Liabilities (IBNR)	3,032
Cumulative Paid Claims and Allocated Claim Adjustment Expenses, Net of Reinsurance	$ 3,931
Minimum | Healthcare Professional Liability claims-made
Claims Development [Line Items]
Initial loss ratio	87.00%
Maximum | Healthcare Professional Liability claims-made
Claims Development [Line Items]
Initial loss ratio	106.00%