Investments (Net Unrealized Gains Losses on Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	$ (164,467)	$ (443,575)
Fixed maturities | Available-for-sale | OTTI
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	591	(1,261)
Fixed maturities | Available-for-sale | All other
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	(162,303)	(454,274)
Equity securities | Available-for-sale
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	4	(347)
Affiliated notes
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	1,040	1,181
Derivatives designated as cash flow hedges
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	(3,378)	11,745
Other investments
Gain (Loss) on Investments [Line Items]
Net unrealized gains (losses) on investments	$ (421)	$ (619)