CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$ 12,176,473,000	$ 12,241,782,000
Fixed maturities, available for sale, allowance for credit loss	11,733,000	313,000	$ 323,000	$ 0
Fixed maturities, held to maturity, fair value	674,743,000	445,033,000
Fixed maturities, held to maturity, allowance for credit loss	0	0
Equity securities, cost	494,356,000	528,864,000
Credit losses associated with commercial mortgage loans	0	0
Allowance for credit losses on premium balances receivable	9,521,000	7,567,000
Allowance for credit losses on reinsurance recoverable for unpaid losses and loss expenses	$ 30,715,000	$ 29,554,000	$ 24,000,000
Common shares, shares issued (in shares)	176,580	176,580
Common shares, shares outstanding (in shares)	84,668	84,774
Treasury shares (in shares)	91,912	91,806

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

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