Investments (Realized Investment Gains Losses Net) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ (35,725)	$ 5,687	$ (2,497,661)	$ 10,006
Fixed maturities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	9,899	(252)	94,834	4,652
Equity securities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	0	0	0	0
Commercial mortgage and other loans
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(422)	(75)	(1,823)	12
Derivatives
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(45,139)	6,014	(2,590,550)	5,342
Short-term investments and cash equivalents
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	104	0	527	0
Other long-term investments
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ (167)	$ 0	$ (649)	$ 0