Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Equity securities, cost	$ 2,904,496
Available for sale equity securities, cost		$ 3,170,673
Debt securities, amortized cost	$ 11,895,850	$ 12,536,772
Common stock, Shares authorized	22,000,000	22,000,000
Common stock, Shares issued	17,459,961	17,459,961
Treasury stock, shares	2,883,452	2,069,461