Derivative Instruments - Derivatives - Fair Value Hedges - Non-qualifying Strategies (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	$ 12	$ (6)	$ (1)	$ (6)
Total other non-qualifying derivatives
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	8	1	(2)	8
Foreign currency swaps and forwards
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	4	(7)	1	(14)
Total foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	4	(7)	1	(14)
Interest rate swaps, swaptions, and futures
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	8	(7)	6	(2)
Credit derivatives that assume credit risk | Credit derivatives that purchase credit protection
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	1	23	0	18
Credit derivatives that assume credit risk | Credit derivatives that assume credit risk
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	0	(16)	(8)	(7)
Equity Options
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(1)	1	0	0
Contingent capital facility put option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	$ 0	$ 0	$ 0	$ (1)