Equity (Components of Net Unrealized Appreciation Depreciation of Balances Carried at Fair Value) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Comprehensive Income Net Of Tax [Line Items]
Fixed maturity securities available-for-sale		$ 32,093,625	$ 29,642,905
Other invested assets		1,591,940	1,298,120
Deferred policy acquisition costs		3,338,605	3,392,437	$ 3,342,575	$ 3,517,796
Accumulated Other Comprehensive Income Loss Change In Component During Period		577,265	(1,028,965)	1,153,224
Change In Net Unrealized Appreciation Depreciation [Member]
Comprehensive Income Net Of Tax [Line Items]
Fixed maturity securities available-for-sale		561,906	(1,055,458)	1,171,996
Other invested assets	[1]	18,900	8,983	(14,292)
Effect On Unrealized Appreciation Depreciation [Member]
Comprehensive Income Net Of Tax [Line Items]
Deferred policy acquisition costs		$ (3,541)	$ 17,510	$ (4,480)

[1] Includes cash flow hedges. See Note 5 for additional information on cash flow hedges.