Derivative Instruments (Financial Statement Classification and Impact of Derivatives Used in Qualifying and Non-qualifying Hedge Relationships) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	$ (160,368)	$ (154,208)	$ (106,625)
Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	9,007	6,819	6,071
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(1,703)	10,110	(8,305)
AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	4,031	39,801	(58,609)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	425	(997)	1,061
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	9,007	6,819	6,071
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(1,698)	10,066	(8,234)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	4,031	39,801	(58,609)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(160,793)	(153,211)	(107,686)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(5)	44	(71)
Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Interest Rate Swaps | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0
Interest Rate Swaps | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0
Interest Rate Swaps | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0
Interest Rate Swaps | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(50)
Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	18,609	(7,688)	(1,565)
Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Currency | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	20	1,475	(1,316)
Currency | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Currency | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Currency | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Currency/Interest Rate | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	425	(997)	1,061
Currency/Interest Rate | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	9,007	6,819	6,071
Currency/Interest Rate | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(1,698)	10,066	(8,234)
Currency/Interest Rate | Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	4,081	39,801	(58,609)
Currency/Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	3,485	6,395	(8,306)
Currency/Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Currency/Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(5)	44	(71)
Currency/Interest Rate | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Credit | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(1)	(2)	(46)
Credit | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Credit | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Credit | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Equity | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	74,068	(27,212)	30,466
Equity | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Equity | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Equity | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Embedded Derivatives | Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	(256,974)	(126,179)	(126,919)
Embedded Derivatives | Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Embedded Derivatives | Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	0	0	0
Embedded Derivatives | Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivative, net	$ 0	$ 0	$ 0