Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	$ (416,909)	$ (59,412)	$ (443,575)
Fixed maturities | Available-for-sale | OTTI
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	(3,334)	12,311	(1,261)
Fixed maturities | Available-for-sale | All other
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	(411,458)	(46,791)	(454,274)
Equity securities | Available-for-sale
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	0	4	(347)
Derivatives designated as cash flow hedges
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	(3,849)	(25,851)	11,745
Affiliated notes
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	658	829	1,181
Other Investments
Gain (Loss) on Securities [Line Items]
Net Unrealized Gains (Losses) on Investments	$ 1,074	$ 86	$ (619)