Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Notional	$ 4,200,893	$ 3,070,256
Gross Fair Value Assets	251,768	77,890
Gross Fair Value Liabilities	(97,802)	(26,862)
Future policy benefits
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(8,530,000)	(5,589,000)
Policyholders' account balances
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	(962,000)	(13,000)
Reinsurance recoverables
Derivative [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative, Net	8,540,000	5,600,000
Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	777,548	719,476
Gross Fair Value Assets	36,551	38,333
Gross Fair Value Liabilities	(12,521)	(16,638)
Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	3,423,345	2,350,780
Gross Fair Value Assets	215,217	39,557
Gross Fair Value Liabilities	(85,281)	(10,224)
Foreign Currency Swaps \| Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	773,933	719,476
Gross Fair Value Assets	36,551	38,333
Gross Fair Value Liabilities	(12,471)	(16,638)
Foreign Currency Swaps \| Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	151,792	98,363
Gross Fair Value Assets	7,563	6,303
Gross Fair Value Liabilities	(1,892)	(2,109)
Interest Rate Swaps \| Derivatives Designated as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	3,615	0
Gross Fair Value Assets	0	0
Gross Fair Value Liabilities	(50)	0
Interest Rate Swaps \| Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	569,925	246,925
Gross Fair Value Assets	33,256	15,665
Gross Fair Value Liabilities	(4,490)	(3,174)
Foreign Currency Forwards \| Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	21,580	23,043
Gross Fair Value Assets	0	277
Gross Fair Value Liabilities	(518)	(20)
Credit Default Swaps \| Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	0	756
Gross Fair Value Assets	0	0
Gross Fair Value Liabilities	0	(9)
Equity Options \| Derivatives Not Qualifying as Hedge Accounting Instruments:
Derivative [Line Items]
Notional	2,680,048	1,981,693
Gross Fair Value Assets	174,398	17,312
Gross Fair Value Liabilities	$ (78,381)	$ (4,912)

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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