Schedule II - Condensed Balance Sheet (Parent Only) Schedule II - Condensed Balance Sheet (Parent Only) (Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Fixed maturity securities available for sale, amortized cost	$ 9,470,795	$ 10,048,100
Equity securities available for sale, cost	$ 450,563	$ 434,875
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	800,000,000	800,000,000
Common stock, shares outstanding (in shares)	65,850,386	69,299,559	71,828,208	78,664,029
Treasury stock, at cost (in shares)	83,523,031	79,338,142
Parent Company
Condensed Financial Statements, Captions [Line Items]
Fixed maturity securities available for sale, amortized cost	$ 143,069	$ 265,433
Equity securities available for sale, cost	$ 4,694	$ 13,014
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	800,000,000	800,000,000
Common stock, shares outstanding (in shares)	65,850,386	69,299,559
Treasury stock, at cost (in shares)	69,299,559	79,338,142