Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Fixed maturities, amortized cost	$ 9,590,337	$ 9,038,158
Equity securities, cost	2,390,184	2,208,834
Senior long-term debt and other debt, estimated fair value	$ 2,842,000	$ 2,403,000