Investment Securities - Amortized Costs, Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale securities
Amortized cost	$ 228,769	$ 198,194
Gross unrealized gains	3,168	3,961
Gross unrealized losses	1,543	477
Fair value	230,394	201,678
Available-for-sale equity securities
Amortized cost		547
Gross unrealized gains		0
Gross unrealized losses		0
Fair value		547
Total available-for-sale securities
Amortized cost		198,741
Gross unrealized gains		3,961
Gross unrealized losses		477
Fair value		202,225
Held-to-maturity securities
Amortized cost	31,434	47,733
Gross unrealized gains	239	1,113
Gross unrealized losses	215	194
Fair value	31,458	48,652
Debt Securities, Available-for-sale and Held-to-maturity [Abstract]
Amortized cost	260,203	246,474
Gross unrealized gains	3,407	5,074
Gross unrealized losses	1,758	671
Fair value	261,852	250,877
Total mortgage-backed securities
Available-for-sale securities
Amortized cost	84,190	85,886
Gross unrealized gains	788	1,141
Gross unrealized losses	1,158	355
Fair value	83,820	86,672
Held-to-maturity securities
Amortized cost	26,610	33,360
Gross unrealized gains	134	559
Gross unrealized losses	200	114
Fair value	26,544	33,805
U.S. government agencies
Available-for-sale securities
Amortized cost	69,026	69,879
Gross unrealized gains	594	736
Gross unrealized losses	974	335
Fair value	68,646	70,280
Held-to-maturity securities
Amortized cost	26,610	27,577
Gross unrealized gains	134	558
Gross unrealized losses	200	40
Fair value	26,544	28,095
Residential: U.S.
Available-for-sale securities
Amortized cost	5,877	8,193
Gross unrealized gains	79	185
Gross unrealized losses	31	14
Fair value	5,925	8,364
Residential: Non-U.S.
Available-for-sale securities
Amortized cost	2,529	2,882
Gross unrealized gains	72	122
Gross unrealized losses	6	1
Fair value	2,595	3,003
Commercial
Available-for-sale securities
Amortized cost	6,758	4,932
Gross unrealized gains	43	98
Gross unrealized losses	147	5
Fair value	6,654	5,025
Held-to-maturity securities
Amortized cost	0	5,783
Gross unrealized gains	0	1
Gross unrealized losses	0	74
Fair value	0	5,710
U.S. Treasury and government agencies
Available-for-sale securities
Amortized cost	55,771	22,510
Gross unrealized gains	366	266
Gross unrealized losses	78	31
Fair value	56,059	22,745
Obligations of U.S. states and municipalities
Available-for-sale securities
Amortized cost	36,221	30,490
Gross unrealized gains	1,582	1,881
Gross unrealized losses	80	33
Fair value	37,723	32,338
Held-to-maturity securities
Amortized cost	4,824	14,373
Gross unrealized gains	105	554
Gross unrealized losses	15	80
Fair value	4,914	14,847
Certificates of deposit
Available-for-sale securities
Amortized cost	75	59
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Fair value	75	59
Non-U.S. government debt securities
Available-for-sale securities
Amortized cost	23,771	26,900
Gross unrealized gains	351	426
Gross unrealized losses	20	32
Fair value	24,102	27,294
Corporate debt securities
Available-for-sale securities
Amortized cost	1,904	2,657
Gross unrealized gains	23	101
Gross unrealized losses	9	1
Fair value	1,918	2,757
Asset-backed securities: Collateralized loan obligations
Available-for-sale securities
Amortized cost	19,612	20,928
Gross unrealized gains	1	69
Gross unrealized losses	176	1
Fair value	19,437	20,996
Asset-backed securities: Other
Available-for-sale securities
Amortized cost	7,225	8,764
Gross unrealized gains	57	77
Gross unrealized losses	22	24
Fair value	7,260	8,817
US government-sponsored and enterprises obligations
Available-for-sale securities
Fair value	50,700	45,800
Held-to-maturity securities
Amortized cost	$ 20,900	$ 22,000

Available-for-sale Securities and Held-to-maturity Securities, Accumulated Gross Unrealized Gain, before Tax

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