Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Fixed maturities, available-for-sale, amortized cost	$ 9,448,840	$ 9,950,773
Equity securities, cost	3,266,735	2,971,856
Senior long-term debt and other debt, estimated fair value	$ 3,907,000	$ 3,030,000