SEGMENT INFORMATION - Gross premiums written (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	$ 7,685,984	$ 6,826,938	$ 6,898,858
Bermuda
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	542,693	602,432	738,258
Ireland
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	1,667,496	1,516,596	1,679,646
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	4,002,748	3,398,108	3,090,547
Lloyd's of London
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	$ 1,473,047	$ 1,309,802	$ 1,390,407