Derivatives, Sold and Purchased Credit Derivatives (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	$ 80	$ 182
Notional amount Protection sold	10,507	11,741
Notional amount Protection purchased with identical underlyings	1,991	3,898
Notional Net protection sold	8,516	7,843
Notional Other protection purchased	19,013	17,082
Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	6,723	6,629
Corporate bonds [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	1	59
Notional amount Protection sold	1,995	2,037
Notional amount Protection purchased with identical underlyings	1,362	1,374
Notional Net protection sold	633	663
Notional Other protection purchased	$ 2,021	$ 1,460
Corporate bonds [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2019	Jan. 01, 2019
Corporate bonds [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2029	Dec. 31, 2027
Corporate bonds [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 472	$ 441
Structured products [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	31	62
Notional amount Protection sold	138	133
Notional amount Protection purchased with identical underlyings	109	121
Notional Net protection sold	29	12
Notional Other protection purchased	$ 113	$ 113
Structured products [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2022	Jan. 01, 2022
Structured products [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2047	Dec. 31, 2047
Structured products [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 133	$ 128
Credit default swap [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	0	1
Notional amount Protection sold	1,897	3,618
Notional amount Protection purchased with identical underlyings	163	1,998
Notional Net protection sold	1,734	1,620
Notional Other protection purchased	$ 3,923	$ 2,896
Credit default swap [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2019	Jan. 01, 2019
Credit default swap [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2029	Dec. 31, 2028
Credit default swap [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 194	$ 582
Commercial [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	38	49
Notional amount Protection sold	342	389
Notional amount Protection purchased with identical underlyings	316	363
Notional Net protection sold	26	26
Notional Other protection purchased	$ 51	$ 51
Commercial [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2047	Jan. 01, 2047
Commercial [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2058	Dec. 31, 2058
Commercial [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 87	$ 109
Asset-backed securities [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	8	9
Notional amount Protection sold	41	42
Notional amount Protection purchased with identical underlyings	41	42
Notional Net protection sold	0	0
Notional Other protection purchased	$ 1	$ 1
Asset-backed securities [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2045	Jan. 01, 2045
Asset-backed securities [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2046	Dec. 31, 2046
Asset-backed securities [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 41	$ 42
Other Credit Derivatives [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Fair value liability	2	2
Notional amount Protection sold	6,094	5,522
Notional amount Protection purchased with identical underlyings	0	0
Notional Net protection sold	6,094	5,522
Notional Other protection purchased	$ 12,904	$ 12,561
Other Credit Derivatives [Member] | Minimum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Jan. 01, 2019	Jan. 01, 2018
Other Credit Derivatives [Member] | Maximum [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Derivative range of maturity dates	Dec. 31, 2048	Dec. 31, 2048
Other Credit Derivatives [Member] | Non-investment grade [Member]
Details of Sold and Purchased Credit Derivatives [Abstract]
Notional amount Protection sold	$ 5,796	$ 5,327