Investments (Other Invested Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Other Investments [Abstract]
Other invested assets	$ 1,591,940	$ 1,298,120
Equity Securities [Member]
Other Investments [Abstract]
Other invested assets	275,361	125,862
Limited Partner [Member]
Other Investments [Abstract]
Other invested assets	687,522	567,697
Gain (Loss) on Derivatives [Member]
Other Investments [Abstract]
Other invested assets	229,108	256,178
Fair Value Option Contractholder Directed Unit Linked Investments [Member]
Other Investments [Abstract]
Other invested assets	190,120	197,547
Other [Member]
Other Investments [Abstract]
Other invested assets	$ 209,829	$ 150,836