Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Equity securities, cost	$ 2,400,563	$ 2,552,722
Debt securities, amortized cost	15,993,207	15,727,143
Allowance for credit losses	$ 1,084	$ 502
Common stock, Shares authorized	22,000,000	22,000,000
Common stock, Shares issued	17,459,961	17,459,961
Treasury stock, shares	4,005,073	3,861,426