Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Amortized cost on fixed maturities trading investments	$ 3,388,418	$ 2,973,276
Cost - equity security trading investments	695,150	648,282
Cost - short-term investments	$ 376,547	$ 494,060
Common Stock
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	70,000,000	70,000,000
Common stock, shares issued (in shares)	55,358,000	55,358,000
Common stock, shares outstanding (in shares)	55,358,000	55,358,000