Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other invested assets	$ 1,532,523	$ 1,591,940
Equity securities
Other invested assets	112,931	275,361
Limited Partner [Member]
Other invested assets	761,739	687,522
Derivatives
Other invested assets	133,405	229,108
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Other invested assets	210,660	190,120
Other
Other invested assets	$ 313,788	$ 209,829