Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fixed maturities, available-for-sale amortized cost	$ 10,119,406	$ 9,655,261
Equity securities, cost	2,758,061	2,732,998
Senior long-term debt and other debt (estimated fair value)	$ 4,096,000	$ 4,367,000