Investments (Realized Investment Gains Losses Net) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ 860,462	$ (170,656)	$ 915,613	$ (111,631)
Fixed maturities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	90,319	1,932	75,395	4,046
Equity securities
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	(1,718)	(2)	(1,718)	(2)
Commercial mortgage and other loans
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	29,429	128	29,991	279
Joint ventures and limited partnerships
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	81	128	(67)	165
Derivatives
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	742,347	(172,883)	811,994	(116,162)
Other
Schedule Of Gain Loss On Investments [Line Items]
Realized investment gains (losses), net	$ 4	$ 41	$ 18	$ 43