Consolidated Balance Sheets (Parenthetical) $ in Thousands	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Fixed maturities, available-for-sale, amortized cost | $	$ 2,628,225	$ 2,400,245
Equity securities, available-for-sale, cost | $	327,911	281,943
Short-term investments, amortized cost | $	$ 143,451	$ 217,743
Preferred stock, par value | $ / shares	$ 0.10	$ 0.10
Preferred stock, authorized shares	1,000,000	1,000,000
Preferred stock, issued shares	0	0
Common stock, par value | $ / shares	$ 0.10	$ 0.10
Common stock, authorized shares	50,000,000	50,000,000
Common stock, issued shares	36,146,899	35,884,538
Treasury stock, shares	7,022,760	7,022,760