Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Amortized cost on fixed maturities trading investments	$ 3,850,850	$ 3,388,418
Cost - equity security trading investments	734,861	695,150
Cost - short-term investments	194,721	376,547
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	$ 301,890	$ 286,023
Common Stock
Common stock, shares authorized (in shares)	70,000,000	70,000,000
Common stock, shares issued (in shares)	55,371,000	55,358,000
Common stock, shares outstanding (in shares)	55,371,000	55,358,000