Derivatives (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Estimated Fair Value Assets	$ 21,788		$ 21,788		$ 14,406
Estimated Fair Value Liabilities	8,352		8,352		7,049
Maximum Amount of Future Payments under Credit Default Swaps	11,664		11,664		10,311
Estimated Fair Value of Credit Default Swaps	140		140		65
Excess securities collateral received on derivatives	554		554		$ 89
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	801	$ (1,833)	$ (4,992)	$ (1,039)
Derivative, Average Remaining Maturity			4 years 6 months		4 years 1 month
Derivative Instrument Detail [Abstract]
Net amounts reclassified into net derivatives gains (losses) on discontinued cash flow hedges	12	(3)	$ 7	0
Hedging exposure to variability in future cash flows for specific length of time			6 years		5 years
Accumulated Other Comprehensive Income Loss	3,600		$ 3,600		$ 2,400
Deferred net gains (losses) expected to be reclassified to earnings			(64)
Amount and Location of Gains (Losses) Reclassified from Accumulated Other Comprehensive Income (Loss) into Income (Loss) (Effective Portion)	$ 0	$ 0	$ 0	$ 0
Immateriality of cash flow effectiveness	0	0	0	0
Cumulative foreign currency translation gain (loss) recorded in accumulated other comprehensive income (loss) for net investment in foreign operations hedges	$ 347		$ 347		1,100
Potential future recoveries available to offset maximum amount of future payments under credit default swaps	30		30		80
Excess securities collateral provided on derivatives	432		432		204
Change in fair value of derivatives excluded from the assessment of hedge effectiveness	(6)	$ (4)	(16)	$ (9)
Securities collateral received which the company is permitted to sell or repledge, amount that has been sold or repledged	0		0
Over the Counter [Member]
Derivatives, Fair Value [Line Items]
Cash collateral on derivative assets	(9,606)		(9,606)		(6,140)
Excess securities collateral received on derivatives	(137)		(137)		(100)
Excess securities collateral provided on derivatives	(185)		(185)		(150)
Exchange-traded
Derivatives, Fair Value [Line Items]
Cash collateral on derivative assets	0		0		0
Excess securities collateral received on derivatives	(960)		(960)		(315)
Excess securities collateral provided on derivatives	(462)		(462)		(224)
Hedge Funds [Member]
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps					20
Estimated Fair Value of Credit Default Swaps					(2)
Ba [Member]
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	155		$ 155		$ 164
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			4 years 4 months		1 year 6 months
Nonperformance Risk [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net derivatives gains (losses)	(224)	$ 253	$ 1,200	$ 222
B
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	226		$ 226		$ 639
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			4 years 4 months		4 years 11 months
Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Estimated Fair Value Assets	333		$ 333		$ 278
Estimated Fair Value Liabilities	(11)		(11)		41
Credit Index Product [Member] | Ba [Member]
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	0		$ 0		$ 100
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			0 years		1 year
Credit Index Product [Member] | B
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	156		$ 156		$ 639
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			5 years 4 months		4 years 11 months
Credit Default Swap [Member] | Ba [Member]
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	155		$ 155		$ 64
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			4 years 4 months		2 years 4 months
Credit Default Swap [Member] | B
Derivatives, Fair Value [Line Items]
Maximum Amount of Future Payments under Credit Default Swaps	$ 70		$ 70		$ 0
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Average Remaining Maturity			2 years 1 month		0 years