Derivative Instruments (Financial Statement Classification and Impact of Derivatives Used in Qualifying and Non-qualifying Hedge Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	$ 272,748	$ 742,347	$ 244,531	$ 811,994
Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	1,580	883	2,768	2,288
Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(2,397)	1,608	(4,815)	(301)
AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(12,452)	6,971	(22,713)	(10,128)
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	0	0	0	0
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	1,580	883	2,768	2,288
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(2,371)	1,655	(4,792)	(244)
Derivatives Designated as Hedge Accounting Instruments: | Cash flow hedges | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(12,452)	6,971	(22,713)	(10,128)
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	0	0	0	0
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	1,580	883	2,768	2,288
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	(2,371)	1,655	(4,792)	(244)
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	(12,452)	6,971	(22,713)	(10,128)
Derivatives Not Qualifying as Hedge Accounting Instruments: | Realized Investment Gains (Losses)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	272,748	742,347	244,531	811,994
Derivatives Not Qualifying as Hedge Accounting Instruments: | Net Investment Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0	0	0
Derivatives Not Qualifying as Hedge Accounting Instruments: | Other Income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	(26)	(47)	(23)	(57)
Derivatives Not Qualifying as Hedge Accounting Instruments: | AOCI
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, gain (loss) on derivatives, net	0	0	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	1,130	1,951	1,632	191,878
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	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	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	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	(580)	1,010	(709)	885
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	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	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	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	(1,070)	7,930	1,058	6,834
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	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	(26)	(47)	(23)	(57)
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	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	(7)	(126)	(38)	(367)
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	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	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	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	4,521	(1,926)	10,442	(5,240)
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	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	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	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	268,754	733,508	232,146	618,004
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	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	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	$ 0	$ 0