Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Available for Sale Securities Amortized Cost
Due in one year or less		$ 12,237
Due after one year through five years		46,603
Due after five years through ten years		62,045
Due after ten years		154,198
Amortized Cost		303,287	$ 292,581
Available for Sale Securities Fair Value
Due in one year or less		12,884
Due after one year through five years		50,603
Due after five years through ten years		67,286
Due after ten years		175,738
Fair Value	[1]	335,254	321,419
Held to Maturity Securities Amortized Cost
Due in one year or less		4
Due after one year through five years		177
Due after five years through ten years		567
Due after ten years		867
Amortized Cost	[1]	2,123	2,144
Held to Maturity Securities Fair Value
Due in one year or less		4
Due after one year through five years		186
Due after five years through ten years		650
Due after ten years		1,130
Fair Value		2,516	2,524
Asset-backed securities
Available for Sale Securities Amortized Cost
Debt Maturities, without single maturity date		11,229
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date		11,410
Held to Maturity Securities Amortized Cost
Debt Maturities, without Single Maturity Date		0
Held to Maturity Securities Fair Value
Debt Maturities, without Single Maturity Date		0
Commercial mortgage-backed securities
Available for Sale Securities Amortized Cost
Debt Maturities, without single maturity date		13,011
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date		13,184
Held to Maturity Securities Amortized Cost
Debt Maturities, without Single Maturity Date		0
Held to Maturity Securities Fair Value
Debt Maturities, without Single Maturity Date		0
Residential mortgage-backed securities
Available for Sale Securities Amortized Cost
Debt Maturities, without single maturity date		3,964
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date		4,149
Held to Maturity Securities Amortized Cost
Debt Maturities, without Single Maturity Date		508
Held to Maturity Securities Fair Value
Debt Maturities, without Single Maturity Date		546
Fixed maturities
Available for Sale Securities Amortized Cost
Amortized Cost		303,287	292,581
Available for Sale Securities Fair Value
Fair Value		335,254	321,419
Held to Maturity Securities Amortized Cost
Amortized Cost		2,123	2,144
Held to Maturity Securities Fair Value
Fair Value		2,516	2,524
Fixed maturities | U.S. corporate private securities
Available for Sale Securities Amortized Cost
Amortized Cost		30,665	29,974
Available for Sale Securities Fair Value
Fair Value		32,760	31,788
Fixed maturities | Asset-backed securities
Available for Sale Securities Amortized Cost
Amortized Cost		11,229	11,759
Available for Sale Securities Fair Value
Fair Value		11,410	11,935
Fixed maturities | Commercial mortgage-backed securities
Available for Sale Securities Amortized Cost
Amortized Cost		13,011	12,589
Available for Sale Securities Fair Value
Fair Value		13,184	12,704
Held to Maturity Securities Amortized Cost
Amortized Cost		0	0
Held to Maturity Securities Fair Value
Fair Value		0	0
Fixed maturities | Residential mortgage-backed securities
Available for Sale Securities Amortized Cost
Amortized Cost		3,964	4,308
Available for Sale Securities Fair Value
Fair Value		4,149	4,532
Held to Maturity Securities Amortized Cost
Amortized Cost		508	573
Held to Maturity Securities Fair Value
Fair Value		546	616
Fixed maturities | Prudential Netting Agreement
Held to Maturity Securities Amortized Cost
Amortized Cost		4,403	4,403
Held to Maturity Securities Fair Value
Fair Value		4,498	4,403
Fixed maturities | Prudential Netting Agreement | U.S. corporate private securities
Available for Sale Securities Amortized Cost
Amortized Cost		1,738	1,456
Available for Sale Securities Fair Value
Fair Value		$ 1,738	$ 1,456

[1] See Note 5 for details of balances associated with variable interest entities.