Derivative Instruments and Hedging Activities - Maximum Potential Payout/Notional of Credit Protection Sold (Details) - Credit Protection Sold - USD ($) $ in Billions	Jun. 30, 2019	Dec. 31, 2018
Credit Derivatives
Maximum potential payout/notional	$ 193	$ 224
Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	36	42
1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	44	51
3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	81	102
Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	32	29
CDS
Credit Derivatives
Maximum potential payout/notional	193	224
CDS protection sold with identical protection purchased	181	210
CDS | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	36	42
CDS | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	44	51
CDS | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	81	102
CDS | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	32	29
Single-name CDS
Credit Derivatives
Maximum potential payout/notional	102	104
Single-name CDS | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	26	32
Single-name CDS | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	31	35
Single-name CDS | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	34	28
Single-name CDS | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	11	9
Single-name CDS | Investment grade
Credit Derivatives
Maximum potential payout/notional	70	73
Single-name CDS | Investment grade | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	17	22
Single-name CDS | Investment grade | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	20	24
Single-name CDS | Investment grade | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	24	19
Single-name CDS | Investment grade | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	9	8
Single-name CDS | Non-investment grade
Credit Derivatives
Maximum potential payout/notional	32	31
Single-name CDS | Non-investment grade | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	9	10
Single-name CDS | Non-investment grade | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	11	11
Single-name CDS | Non-investment grade | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	10	9
Single-name CDS | Non-investment grade | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	2	1
Index and basket CDS
Credit Derivatives
Maximum potential payout/notional	91	120
Index and basket CDS | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	10	10
Index and basket CDS | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	13	16
Index and basket CDS | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	47	74
Index and basket CDS | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	21	20
Index and basket CDS | Investment grade
Credit Derivatives
Maximum potential payout/notional	54	83
Index and basket CDS | Investment grade | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	3	5
Index and basket CDS | Investment grade | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	7	10
Index and basket CDS | Investment grade | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	34	61
Index and basket CDS | Investment grade | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	10	7
Index and basket CDS | Non-investment grade
Credit Derivatives
Maximum potential payout/notional	37	37
Index and basket CDS | Non-investment grade | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	7	5
Index and basket CDS | Non-investment grade | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	6	6
Index and basket CDS | Non-investment grade | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	13	13
Index and basket CDS | Non-investment grade | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	11	13
Other credit contracts
Credit Derivatives
Maximum potential payout/notional	0	0
Other credit contracts | Less Than 1 (Year)
Credit Derivatives
Maximum potential payout/notional	0	0
Other credit contracts | 1 - 3 (Years)
Credit Derivatives
Maximum potential payout/notional	0	0
Other credit contracts | 3 - 5 (Years)
Credit Derivatives
Maximum potential payout/notional	0	0
Other credit contracts | Over 5 (Years)
Credit Derivatives
Maximum potential payout/notional	$ 0	$ 0