SEGMENT INFORMATION - Summary of Net Premiums Earned by Segment and Line of Business (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Information [Line Items]
Net premiums earned	$ 5,160,326	$ 4,709,850	$ 4,371,309
Operating Segments
Segment Information [Line Items]
Net premiums earned	5,160,326	4,709,850	4,371,309
Operating Segments | Insurance
Segment Information [Line Items]
Net premiums earned	3,134,155	2,651,339	2,299,038
Operating Segments | Insurance | Professional lines
Segment Information [Line Items]
Net premiums earned	817,924	646,390	509,448
Operating Segments | Insurance | Property
Segment Information [Line Items]
Net premiums earned	755,986	711,297	653,186
Operating Segments | Insurance | Liability
Segment Information [Line Items]
Net premiums earned	459,775	354,787	315,434
Operating Segments | Insurance | Cyber
Segment Information [Line Items]
Net premiums earned	309,004	252,077	206,720
Operating Segments | Insurance | Marine and aviation
Segment Information [Line Items]
Net premiums earned	479,499	439,050	364,656
Operating Segments | Insurance | Accident and health
Segment Information [Line Items]
Net premiums earned	209,548	151,133	143,725
Operating Segments | Insurance | Credit and political risk
Segment Information [Line Items]
Net premiums earned	102,419	96,605	105,869
Operating Segments | Reinsurance
Segment Information [Line Items]
Net premiums earned	2,026,171	2,058,511	2,072,271
Operating Segments | Reinsurance | Run Off Lines
Segment Information [Line Items]
Net premiums earned	322,339	498,105	561,779
Operating Segments | Reinsurance | Professional lines
Segment Information [Line Items]
Net premiums earned	250,911	220,448	207,605
Operating Segments | Reinsurance | Property | Run Off Lines
Segment Information [Line Items]
Net premiums earned	135,480	231,092	256,324
Operating Segments | Reinsurance | Liability
Segment Information [Line Items]
Net premiums earned	484,681	431,596	397,894
Operating Segments | Reinsurance | Marine and aviation
Segment Information [Line Items]
Net premiums earned	78,504	58,775	53,513
Operating Segments | Reinsurance | Accident and health
Segment Information [Line Items]
Net premiums earned	368,747	361,196	333,997
Operating Segments | Reinsurance | Credit and surety
Segment Information [Line Items]
Net premiums earned	192,926	158,549	187,722
Operating Segments | Reinsurance | Motor
Segment Information [Line Items]
Net premiums earned	205,774	247,099	256,064
Operating Segments | Reinsurance | Agriculture
Segment Information [Line Items]
Net premiums earned	122,289	82,743	73,697
Operating Segments | Reinsurance | Catastrophe | Run Off Lines
Segment Information [Line Items]
Net premiums earned	156,232	238,775	244,934
Operating Segments | Reinsurance | Engineering | Run Off Lines
Segment Information [Line Items]
Net premiums earned	$ 30,627	$ 28,238	$ 60,521