Derivative Instruments (Financial Statement Classification and Impact of Derivatives Used in Qualifying and Non-qualifying Hedge Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	$ 93,457	$ (44,477)
Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	2,626	2,069
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	8,886	(1,514)
AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	98,070	(6,654)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	339	(160)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	2,626	2,069
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	8,828	(1,515)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	98,070	(6,654)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Interest Rate | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(45)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Interest Rate | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(3)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Interest Rate | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Interest Rate | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	300
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	384	(160)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	2,629	2,069
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	8,828	(1,515)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Currency/Interest Rate | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	97,770	(6,654)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	93,118	(44,317)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	58	1
Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	30,506	7,616
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Interest Rate | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	1,471	(20)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	19,333	1,430
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	58	1
Derivatives Not Qualifying as Hedge Accounting Instruments: | Currency/Interest Rate | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	(1)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Credit | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(74,944)	28,863
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Equity | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivatives | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	116,752	(82,205)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivatives | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivatives | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Embedded Derivatives | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	$ 0	$ 0