Derivatives - Fair Value Hedges - Non-qualifying Strategies (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	$ (6)	$ 74	$ (7)
Foreign currency swaps and forwards
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(14)	83	13
Interest rate swaps, swaptions and futures
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(5)	1	(8)
Credit derivatives | Credit derivatives that purchase credit protection
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	28	(17)	5
Credit derivatives | Credit derivatives that assume credit risk
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(7)	28	(7)
Equity index options
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(7)	(15)	0
Commodity options
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	0	0	(4)
Contingent capital facility put option
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	(1)	(6)	(6)
Total other non-qualifying derivatives
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Non-qualifying foreign currency derivatives	$ 8	$ (9)	$ (20)