CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 12,419,905	$ 12,634,254
Fixed maturities, available for sale, allowance for credit loss	3,938	10,759	$ 11,733	$ 313
Fixed maturities, held to maturity, fair value	436,751	675,851
Fixed maturities, held to maturity, allowance for credit loss	0	0
Equity securities, cost	520,743	543,833
Allowance for expected credit losses	23,378	6,220	0	$ 0
Allowance for credit losses on premium balances receivable	17,339	11,997	9,521
Allowance for credit losses on reinsurance recoverable for unpaid losses and loss expenses	$ 43,445	$ 36,611	$ 30,715
Common shares, shares issued (in shares)	176,580	176,580
Common shares, shares outstanding (in shares)	82,984	85,286
Treasury shares (in shares)	93,596	91,294