Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Fixed-maturities available for sale, amortized cost	$ 5,655,280	$ 5,587,261
Trading securities amortized cost	112,636	122,472
Equity securities, cost	165,165	162,899
Reinvested cash collateral held under securities lending agreements	86,077	99,735
Reinsurance recoverables, paid losses	$ 21	$ 18
Common stock, par or stated value per share (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	485,000	485,000
Common stock, shares, issued (in shares)	176,032	176,509
Common stock, shares, outstanding (in shares)	156,547	157,056
Treasury stock, shares (in shares)	19,485	19,453