Segment Reporting - Schedule of Gross Premiums Written Allocated to the Territory of Coverage Exposure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	$ 9,213,540	$ 7,833,798	$ 5,806,165
Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	3,734,241	3,958,724	2,999,142
Property | U.S. and Caribbean
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	2,343,830	2,257,088	1,683,538
Property | Worldwide
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	1,053,369	1,188,737	889,917
Property | Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	62,998	253,678	189,587
Property | Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	104,767	114,981	102,228
Property | Worldwide (excluding U.S.)
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	37,436	34,742	62,058
Property | Australia and New Zealand
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	86,080	69,188	40,243
Property | Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	45,761	40,310	31,571
Casualty and Specialty
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	5,479,299	3,875,074	2,807,023
Casualty and Specialty | U.S. and Caribbean
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	2,556,466	1,721,663	1,248,981
Casualty and Specialty | Worldwide
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	2,328,030	1,746,450	1,315,386
Casualty and Specialty | Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	327,831	217,721	121,369
Casualty and Specialty | Worldwide (excluding U.S.)
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	177,746	108,376	56,225
Casualty and Specialty | Australia and New Zealand
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	35,973	29,001	12,429
Casualty and Specialty | Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written (Note 6)	$ 53,253	$ 51,863	$ 52,633