Consolidated Balance Sheets Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Fixed maturity securities, allowance for credit loss	$ 26,531	$ 22,625
Fixed maturity securities, amortized cost	16,838,703	16,471,304
Cumulative effect adjustment resulting from changes in accounting principles	1,429	1,718
Cumulative effect adjustment resulting from changes in accounting principles	28,236	25,218
Reinsurance recoverable, allowance for credit loss	$ 7,655	$ 7,713
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock issued (in shares)	5,000,000	5,000,000
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollar per share)	$ 0.20	$ 0.20
Common shares authorized (in shares)	750,000,000	750,000,000
Common shares issued (in shares)	265,186,251	265,170,882
Common shares outstanding (in shares)	265,186,251	265,170,882
Treasury stock issued at cost (in shares)	263,828,377	263,843,868