Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Notional	$ 157,662,666	$ 20,673,388
Assets	12,678,048	136,775
Liabilities	(3,625,754)	(25,277)
Embedded Derivative, Fair Value of Embedded Derivative, Net	(12,327,000)	(3,134,000)
Future Policy Benefits
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(12,327,000)	(3,134,000)
Reinsurance Recoverables
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	346,000	3,013,000
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	367,928	115,358
Assets	35,322	15,910
Liabilities	(1,903)	(206)
Derivatives Designated as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	367,928	115,358
Assets	35,322	15,910
Liabilities	(1,903)	(206)
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	157,294,738	20,558,030
Assets	12,642,726	120,865
Liabilities	(3,623,851)	(25,071)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Swaps
Derivative [Line Items]
Notional	128,121	77,729
Assets	16,710	11,220
Liabilities	(179)	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Futures
Derivative [Line Items]
Notional	3,318,000	0
Assets	0	0
Liabilities	(30,069)	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Swaps
Derivative [Line Items]
Notional	93,630,825	1,872,750
Assets	11,765,069	84,817
Liabilities	(3,132,401)	(13,452)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Options
Derivative [Line Items]
Notional	13,905,000	100,000
Assets	690,424	9,431
Liabilities	(93,364)	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate Forwards
Derivative [Line Items]
Notional	498,498	0
Assets	38,890	0
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Foreign Currency Forwards
Derivative [Line Items]
Notional	5,985	2,752
Assets	228	23
Liabilities	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Futures
Derivative [Line Items]
Notional	3,422,703	0
Assets	0	0
Liabilities	(38,318)	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Total Return Swaps
Derivative [Line Items]
Notional	18,745,844	217,999
Assets	70,397	320
Liabilities	(231,123)	(3,626)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity Options
Derivative [Line Items]
Notional	23,639,762	18,286,800
Assets	61,008	15,054
Liabilities	$ (98,397)	$ (7,993)