Derivative Instruments (Gross Notional Amount and Fair Value of Derivatives Contracts) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 35,064	$ 14,386
Derivative Liability, Fair Value, Gross Liability	(13,285)	(7,536)
Derivative, Notional Amount	400,233	379,860
Net Embedded Derivative Liability	(28,769)	(14,035)
Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5,164	2,121
Derivative Liability, Fair Value, Gross Liability	(169)	(433)
Derivative, Notional Amount	28,067	27,669
Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,239	628
Derivative Liability, Fair Value, Gross Liability	(106)	(73)
Derivative, Notional Amount	3,232	3,257
Designated as Hedging Instrument | Interest Rate Forward
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	51	4
Derivative Liability, Fair Value, Gross Liability	0	(1)
Derivative, Notional Amount	205	205
Designated as Hedging Instrument | Foreign Exchange Forward
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	79	22
Derivative Liability, Fair Value, Gross Liability	(3)	(57)
Derivative, Notional Amount	1,442	1,461
Designated as Hedging Instrument | Currency Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3,795	1,467
Derivative Liability, Fair Value, Gross Liability	(60)	(302)
Derivative, Notional Amount	23,188	22,746
Not Designated as Hedging Instrument
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	29,900	12,265
Derivative Liability, Fair Value, Gross Liability	(13,116)	(7,103)
Derivative, Notional Amount	372,166	352,191
Not Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	22,455	10,249
Derivative Liability, Fair Value, Gross Liability	(11,144)	(4,861)
Derivative, Notional Amount	152,646	141,162
Not Designated as Hedging Instrument | Interest Rate Forward
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	82	18
Derivative Liability, Fair Value, Gross Liability	0	(3)
Derivative, Notional Amount	2,821	2,218
Not Designated as Hedging Instrument | Foreign Exchange Forward
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	458	208
Derivative Liability, Fair Value, Gross Liability	(163)	(214)
Derivative, Notional Amount	27,940	26,604
Not Designated as Hedging Instrument | Foreign Exchange Option
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	0	0
Not Designated as Hedging Instrument | Currency Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,409	740
Derivative Liability, Fair Value, Gross Liability	(397)	(345)
Derivative, Notional Amount	13,107	13,874
Not Designated as Hedging Instrument | Interest Rate Future
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	42	4
Derivative Liability, Fair Value, Gross Liability	(132)	(38)
Derivative, Notional Amount	18,595	17,095
Not Designated as Hedging Instrument | Interest Rate Option
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,102	339
Derivative Liability, Fair Value, Gross Liability	(328)	(238)
Derivative, Notional Amount	16,343	16,496
Not Designated as Hedging Instrument | Credit Default Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	21
Derivative Liability, Fair Value, Gross Liability	(29)	0
Derivative, Notional Amount	1,659	798
Not Designated as Hedging Instrument | Equity Future
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	18	0
Derivative Liability, Fair Value, Gross Liability	(1)	(3)
Derivative, Notional Amount	4,804	1,802
Not Designated as Hedging Instrument | Equity Option
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	428	679
Derivative Liability, Fair Value, Gross Liability	(546)	(765)
Derivative, Notional Amount	28,769	32,657
Not Designated as Hedging Instrument | Total Return Swap
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,903	6
Derivative Liability, Fair Value, Gross Liability	(376)	(636)
Derivative, Notional Amount	23,241	18,218
Not Designated as Hedging Instrument | Other Contract
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	0
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	1,257	1,258
Not Designated as Hedging Instrument | Synthetic Gics
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	0	0
Derivative, Notional Amount	$ 80,984	$ 80,009