Fair Value of Assets and Liabilities (Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	$ 867	$ 1,148
Netting	(13,519)	(9,331)
Total derivative liabilities	831	127
Netting	(6,705)	(5,281)
Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	11,243	6,366
Total derivative liabilities	5,214	3,820
Currency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	230	273
Total derivative liabilities	271	140
Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	21	33
Total derivative liabilities	0	23
Currency/Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	2,207	2,292
Total derivative liabilities	647	778
Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	685	1,515
Total derivative liabilities	1,404	647
Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	6	23
Total derivative liabilities	41	9
Level 1 | Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	4	23
Total derivative liabilities	38	2
Level 1 | Currency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 1 | Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 1 | Currency/Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 1 | Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	2	0
Total derivative liabilities	3	7
Level 1 | Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	14,379	10,454
Total derivative liabilities	7,495	5,399
Level 2 | Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	11,238	6,341
Total derivative liabilities	5,176	3,818
Level 2 | Currency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	230	273
Total derivative liabilities	271	140
Level 2 | Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	21	33
Total derivative liabilities	0	23
Level 2 | Currency/Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	2,207	2,292
Total derivative liabilities	647	778
Level 2 | Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	683	1,515
Total derivative liabilities	1,401	640
Level 2 | Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	1	2
Total derivative liabilities	0	0
Level 3 | Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	1	2
Total derivative liabilities	0	0
Level 3 | Currency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 3 | Credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 3 | Currency/Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 3 | Equity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	0	0
Level 3 | Commodity
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total derivative assets	0	0
Total derivative liabilities	$ 0	$ 0