Investment Securities - Amortized Cost and Estimated Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Available-for-sale securities, Amortized cost
Due in one year or less	$ 19,190
Due after one year through five years	94,881
Due after five years through 10 years	22,344
Due after 10 years	95,489
Amortized cost	231,904
Available-for-sale securities, Fair value
Due in one year or less	19,155
Due after one year through five years	91,255
Due after five years through 10 years	21,531
Due after 10 years	90,128
Fair value	$ 222,069	$ 308,525
Available-for-sale securities, Average yield
Due in one year or less	1.70%
Due after one year through five years	0.75%
Due after five years through 10 years	1.93%
Due after 10 years	2.77%
Average yield	1.78%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 24,373
Due after one year through five years	133,885
Due after five years through 10 years	98,966
Due after 10 years	184,472
Amortized cost	441,696
Total held-to-maturity securities, Fair value
Due in one year or less	24,162
Due after one year through five years	128,239
Due after five years through 10 years	90,085
Due after 10 years	173,101
Fair value	$ 415,587	362,628
Total held-to-maturity securities, Average yield
Due in one year or less	0.63%
Due after one year through five years	0.69%
Due after five years through 10 years	1.56%
Due after 10 years	2.73%
Average yield	1.73%
Supplemental information
US government agencies and US government sponsored enterprises residential MBS estimated duration	8 years
US government agencies and US government sponsored enterprises residential collateralized mortgage obligations estimated duration	7 years
U.S. nonagency residential collateralized mortgage obligations estimated duration	6 years
Minimum
Supplemental information
Due period of mortgage-backed securities and collateralized mortgage obligations	10 years
Mortgage-backed securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 2
Due after one year through five years	3,358
Due after five years through 10 years	4,197
Due after 10 years	68,765
Amortized cost	76,322
Available-for-sale securities, Fair value
Due in one year or less	2
Due after one year through five years	3,197
Due after five years through 10 years	4,296
Due after 10 years	63,822
Fair value	$ 71,317	83,562
Available-for-sale securities, Average yield
Due in one year or less	0.23%
Due after one year through five years	1.08%
Due after five years through 10 years	2.56%
Due after 10 years	2.73%
Average yield	2.64%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	1,736
Due after five years through 10 years	11,890
Due after 10 years	124,754
Amortized cost	138,380
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	1,652
Due after five years through 10 years	10,975
Due after 10 years	115,640
Fair value	$ 128,267	114,001
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	1.99%
Due after five years through 10 years	2.44%
Due after 10 years	2.78%
Average yield	2.74%
U.S. Treasury and government agencies
Available-for-sale securities, Amortized cost
Due in one year or less	$ 12,135
Due after one year through five years	84,714
Due after five years through 10 years	10,105
Due after 10 years	6,857
Amortized cost	113,811
Available-for-sale securities, Fair value
Due in one year or less	12,106
Due after one year through five years	81,398
Due after five years through 10 years	9,460
Due after 10 years	7,020
Fair value	$ 109,984	177,463
Available-for-sale securities, Average yield
Due in one year or less	1.56%
Due after one year through five years	0.54%
Due after five years through 10 years	1.60%
Due after 10 years	1.89%
Average yield	0.83%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 24,373
Due after one year through five years	132,070
Due after five years through 10 years	69,919
Due after 10 years	0
Amortized cost	226,362
Total held-to-maturity securities, Fair value
Due in one year or less	24,162
Due after one year through five years	126,512
Due after five years through 10 years	62,182
Due after 10 years	0
Fair value	$ 212,856	183,270
Total held-to-maturity securities, Average yield
Due in one year or less	0.63%
Due after one year through five years	0.67%
Due after five years through 10 years	1.25%
Due after 10 years	0.00%
Average yield	0.84%
Obligations of U.S. states and municipalities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 17
Due after one year through five years	132
Due after five years through 10 years	801
Due after 10 years	9,431
Amortized cost	10,381
Available-for-sale securities, Fair value
Due in one year or less	17
Due after one year through five years	132
Due after five years through 10 years	812
Due after 10 years	9,172
Fair value	$ 10,133	15,860
Available-for-sale securities, Average yield
Due in one year or less	5.75%
Due after one year through five years	4.91%
Due after five years through 10 years	4.71%
Due after 10 years	4.32%
Average yield	4.36%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	79
Due after five years through 10 years	2,014
Due after 10 years	17,111
Amortized cost	19,204
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	75
Due after five years through 10 years	2,000
Due after 10 years	16,231
Fair value	$ 18,306	14,394
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	2.96%
Due after five years through 10 years	3.96%
Due after 10 years	4.13%
Average yield	4.10%
Non-U.S. government debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 6,924
Due after one year through five years	4,608
Due after five years through 10 years	3,530
Due after 10 years	1,161
Amortized cost	16,223
Available-for-sale securities, Fair value
Due in one year or less	6,920
Due after one year through five years	4,507
Due after five years through 10 years	3,315
Due after 10 years	1,066
Fair value	$ 15,808	16,209
Available-for-sale securities, Average yield
Due in one year or less	1.94%
Due after one year through five years	2.59%
Due after five years through 10 years	1.30%
Due after 10 years	1.18%
Average yield	1.93%
Corporate debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	339
Due after five years through 10 years	14
Due after 10 years	0
Amortized cost	353
Available-for-sale securities, Fair value
Due in one year or less	0
Due after one year through five years	306
Due after five years through 10 years	13
Due after 10 years	0
Fair value	$ 319	$ 321
Available-for-sale securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	12.26%
Due after five years through 10 years	2.33%
Due after 10 years	0.00%
Average yield	11.86%
Asset-backed securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 112
Due after one year through five years	1,730
Due after five years through 10 years	3,697
Due after 10 years	9,275
Amortized cost	14,814
Available-for-sale securities, Fair value
Due in one year or less	110
Due after one year through five years	1,715
Due after five years through 10 years	3,635
Due after 10 years	9,048
Fair value	$ 14,508
Available-for-sale securities, Average yield
Due in one year or less	1.88%
Due after one year through five years	2.99%
Due after five years through 10 years	2.09%
Due after 10 years	2.38%
Average yield	2.37%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	0
Due after five years through 10 years	15,143
Due after 10 years	42,607
Amortized cost	57,750
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	0
Due after five years through 10 years	14,928
Due after 10 years	41,230
Fair value	$ 56,158
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	0.00%
Due after five years through 10 years	2.01%
Due after 10 years	2.02%
Average yield	2.02%