Investments (Realized Gains (Losses)) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Held to maturity debt securities:      
Real estate $ 2,950 $ 0 $ 955
Mortgage loans 0 0 0
Other 0 0 (478)
Other net investment gains (losses) 13,070 7,461 11,755
Debt Securities      
Available for sale debt securities:      
Realized gains on disposal 2,644 3,378 7,795
Realized losses on disposal (29) (74) (22)
Held to maturity debt securities:      
Realized gains on redemption 6,940 4,027 3,453
Realized losses on redemption (137) (25) (17)
Equity securities      
Held to maturity debt securities:      
Equity securities realized gains $ 702 $ 155 $ 69