SCHEDULE I - SUMMARY OF INVESTMENTS - OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) $ in Thousands	Dec. 31, 2024 USD ($)
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	$ 14,587,300
Amount shown on the balance sheet	15,042,062
Fixed maturities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	12,419,905
Fair value	12,152,753
Amount shown on the balance sheet	12,152,753
Fixed maturities | U.S. government and agency
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	2,830,111
Fair value	2,802,986
Amount shown on the balance sheet	2,802,986
Fixed maturities | Non-U.S. government
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	753,315
Fair value	729,939
Amount shown on the balance sheet	729,939
Fixed maturities | Corporate debt
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	4,941,510
Fair value	4,842,190
Amount shown on the balance sheet	4,842,190
Fixed maturities | Agency RMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	1,245,681
Fair value	1,184,845
Amount shown on the balance sheet	1,184,845
Fixed maturities | CMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	852,534
Fair value	819,608
Amount shown on the balance sheet	819,608
Fixed maturities | Non-agency RMBS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	132,116
Fair value	122,536
Amount shown on the balance sheet	122,536
Fixed maturities | ABS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	1,547,350
Fair value	1,539,832
Amount shown on the balance sheet	1,539,832
Fixed maturities | Municipals
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	117,288
Fair value	110,817
Amount shown on the balance sheet	110,817
Fixed maturities, held to maturity, at amortized cost
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	443,400
Fair value	436,751
Amount shown on the balance sheet	443,400
Fixed maturities, held to maturity, at amortized cost | Corporate debt
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	122,706
Fair value	115,617
Amount shown on the balance sheet	122,706
Fixed maturities, held to maturity, at amortized cost | ABS
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Amortized cost	320,694
Fair value	321,134
Amount shown on the balance sheet	320,694
Mortgage loans
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	505,697
Amount shown on the balance sheet	505,697
Short-term investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	223,666
Amount shown on the balance sheet	223,666
Equity securities
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	579,274
Amount shown on the balance sheet	579,274
Other investments, at fair value
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	689,159
Amount shown on the balance sheet	930,278
Equity method investments
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Line Items]
Fair value	0
Amount shown on the balance sheet	$ 206,994