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	$ 250,456	$ 112,432
Fixed maturities | Available-for-sale | OTTI
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	946	4,883
Fixed maturities | Available-for-sale | All other
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	221,783	59,755
Equity securities | Available-for-sale
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	1,689	366
Derivatives designated as cash flow hedges
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	18,218	40,931
Affiliated notes
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	6,105	5,056
Other investments
Gain (Loss) on Investments [Line Items]
Net Unrealized Gains (Losses) on Investments	$ 1,715	$ 1,441