LOSS AND LOSS ADJUSTMENT RESERVES - (Schedule of Incurred Losses and ALAE, Net of Reinsurance) (Details) $ in Thousands	Dec. 31, 2021 USD ($) reported_claim	Dec. 31, 2020 USD ($)	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 ($)	Dec. 31, 2012 USD ($)
Homeowners
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 1,614,678
Homeowners | 2012
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	26,935	$ 26,984	$ 26,951	$ 26,836	$ 26,356	$ 25,889	$ 24,468	$ 24,186	$ 23,301	$ 23,032
IBNR & development on reported claims	$ 27
Cumulative number of reported claims | reported_claim	2,692,000
Homeowners | 2013
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 38,141	38,088	37,978	37,880	37,185	35,859	35,834	42,021	43,807
IBNR & development on reported claims	$ 28
Cumulative number of reported claims | reported_claim	3,443,000
Homeowners | 2014
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 62,533	62,535	62,043	61,817	62,206	61,770	63,300	64,312
IBNR & development on reported claims	$ 488
Cumulative number of reported claims | reported_claim	7,656,000
Homeowners | 2015
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 96,189	96,144	94,703	94,760	95,129	92,411	99,497
IBNR & development on reported claims	$ 1,203
Cumulative number of reported claims | reported_claim	13,228,000
Homeowners | 2016
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 156,493	156,316	157,880	158,764	162,043	171,264
IBNR & development on reported claims	$ 2,180
Cumulative number of reported claims | reported_claim	23,996,000
Homeowners | 2017
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 178,890	179,327	188,548	192,769	202,844
IBNR & development on reported claims	$ 48,811
Cumulative number of reported claims | reported_claim	67,453,000
Homeowners | 2018
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 218,267	216,570	213,128	210,158
IBNR & development on reported claims	$ 19,174
Cumulative number of reported claims | reported_claim	38,289,000
Homeowners | 2019
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 260,089	261,541	257,644
IBNR & development on reported claims	$ 10,861
Cumulative number of reported claims | reported_claim	22,774,000
Homeowners | 2020
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 349,456	342,119
IBNR & development on reported claims	$ 125,767
Cumulative number of reported claims | reported_claim	71,508,000
Homeowners | 2021
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 227,685
IBNR & development on reported claims	$ 302,033
Cumulative number of reported claims | reported_claim	23,296,000
Commercial general liability
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 62,455
Commercial general liability | 2012
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	6,430	6,431	5,109	4,509	4,346	4,658	4,700	4,801	4,952	5,279
IBNR & development on reported claims	$ 926
Cumulative number of reported claims | reported_claim	854
Commercial general liability | 2013
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 7,588	7,588	5,984	5,580	5,704	5,502	5,221	5,069	7,095
IBNR & development on reported claims	$ 913
Cumulative number of reported claims | reported_claim	967
Commercial general liability | 2014
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 9,027	9,028	6,697	6,348	6,620	6,384	7,709	7,475
IBNR & development on reported claims	$ 694
Cumulative number of reported claims | reported_claim	1,012
Commercial general liability | 2015
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 9,141	9,141	7,947	5,377	6,020	7,008	8,082
IBNR & development on reported claims	$ 1,597
Cumulative number of reported claims | reported_claim	966
Commercial general liability | 2016
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 11,903	12,267	8,502	6,561	5,809	10,727
IBNR & development on reported claims	$ 4,525
Cumulative number of reported claims | reported_claim	922
Commercial general liability | 2017
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 8,518	8,519	6,558	7,853	8,289
IBNR & development on reported claims	$ 2,675
Cumulative number of reported claims | reported_claim	642
Commercial general liability | 2018
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 7,276	7,280	6,233	6,553
IBNR & development on reported claims	$ 2,801
Cumulative number of reported claims | reported_claim	456
Commercial general liability | 2019
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 2,487	2,535	1,604
IBNR & development on reported claims	$ 944
Cumulative number of reported claims | reported_claim	79
Commercial general liability | 2020
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 68	37
IBNR & development on reported claims	$ 0
Cumulative number of reported claims | reported_claim	8
Commercial general liability | 2021
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 17
IBNR & development on reported claims	$ 0
Cumulative number of reported claims | reported_claim	4
Automobile
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 65,175
Automobile | 2012
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	1,447	1,448	1,444	1,448	1,491	1,455	1,424	1,717	1,741	$ 1,735
IBNR & development on reported claims	$ 4
Cumulative number of reported claims | reported_claim	824
Automobile | 2013
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 2,128	2,127	2,127	2,123	2,161	1,829	1,826	1,863	$ 1,517
IBNR & development on reported claims	$ 6
Cumulative number of reported claims | reported_claim	3,472
Automobile | 2014
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 4,410	4,413	4,417	4,379	4,315	3,551	3,213	$ 2,038
IBNR & development on reported claims	$ 4
Cumulative number of reported claims | reported_claim	6,021
Automobile | 2015
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 2,945	2,944	2,915	2,878	2,781	2,882	$ 3,045
IBNR & development on reported claims	$ 10
Cumulative number of reported claims | reported_claim	6,561
Automobile | 2016
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 25,930	25,923	25,918	24,346	20,205	$ 13,414
IBNR & development on reported claims	$ 34
Cumulative number of reported claims | reported_claim	76,660
Automobile | 2017
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 24,253	24,669	24,579	22,472	$ 20,411
IBNR & development on reported claims	$ 169
Cumulative number of reported claims | reported_claim	61,751
Automobile | 2018
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 4,062	4,439	4,623	$ 3,513
IBNR & development on reported claims	$ 104
Cumulative number of reported claims | reported_claim	10,937
Automobile | 2019
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 0	0	$ (3)
IBNR & development on reported claims	$ 2
Cumulative number of reported claims | reported_claim	103
Automobile | 2020
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 0	$ 0
IBNR & development on reported claims	$ 0
Cumulative number of reported claims | reported_claim	6
Automobile | 2021
Claims Development [Line Items]
Incurred, claims and allocated claim adjustment expenses, net of reinsurance	$ 0
IBNR & development on reported claims	$ 0
Cumulative number of reported claims | reported_claim	6