Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Other invested assets	$ 1,498,370	$ 1,591,940
Equity securities
Other invested assets	104,277	275,361
Limited Partner [Member]
Other invested assets	746,573	687,522
Derivatives
Other invested assets	158,048	229,108
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Other invested assets	204,630	190,120
Other
Other invested assets	$ 284,842	$ 209,829