Investment Securities - Amortized Cost and Estimated Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Available-for-sale securities, Amortized cost
Due in one year or less	$ 61,239
Due after one year through five years	270,187
Due after five years through 10 years	90,249
Due after 10 years	130,328
Amortized cost	552,003
Available-for-sale securities, Fair value
Due in one year or less	61,341
Due after one year through five years	270,010
Due after five years through 10 years	89,948
Due after 10 years	127,738
Fair value	$ 549,037	$ 507,198
Available-for-sale securities, Average yield
Due in one year or less	4.00%
Due after one year through five years	4.00%
Due after five years through 10 years	4.08%
Due after 10 years	4.73%
Average yield	4.18%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 11,119
Due after one year through five years	128,138
Due after five years through 10 years	27,673
Due after 10 years	105,268
Amortized cost	272,198
Total held-to-maturity securities, Fair value
Due in one year or less	11,021
Due after one year through five years	121,962
Due after five years through 10 years	26,204
Due after 10 years	95,326
Fair value	$ 254,513	253,344
Total held-to-maturity securities, Average yield
Due in one year or less	2.66%
Due after one year through five years	2.61%
Due after five years through 10 years	3.16%
Due after 10 years	3.15%
Average yield	2.88%
Supplemental information
Available for sale securities allowance for credit losses	$ 22
Unallocated portfolio layer fair value hedge basis adjustments	179
Held-to-maturity securities allowance for credit losses	$ 56
US government agencies and US government sponsored enterprises residential MBS estimated duration	7 years
Agency residential collateralized mortgage obligations estimated duration	6 years
Nonagency residential collateralized mortgage obligations estimated duration	4 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	$ 949
Due after one year through five years	11,722
Due after five years through 10 years	4,770
Due after 10 years	80,716
Amortized cost	98,157
Available-for-sale securities, Fair value
Due in one year or less	943
Due after one year through five years	11,823
Due after five years through 10 years	4,808
Due after 10 years	79,109
Fair value	$ 96,683	101,447
Available-for-sale securities, Average yield
Due in one year or less	2.84%
Due after one year through five years	4.55%
Due after five years through 10 years	4.52%
Due after 10 years	4.65%
Average yield	4.61%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 946
Due after one year through five years	8,930
Due after five years through 10 years	5,004
Due after 10 years	85,645
Amortized cost	100,525
Total held-to-maturity securities, Fair value
Due in one year or less	937
Due after one year through five years	8,429
Due after five years through 10 years	4,596
Due after 10 years	76,344
Fair value	$ 90,306	93,186
Total held-to-maturity securities, Average yield
Due in one year or less	2.17%
Due after one year through five years	2.46%
Due after five years through 10 years	3.24%
Due after 10 years	2.89%
Average yield	2.86%
U.S. Treasury and government agencies
Available-for-sale securities, Amortized cost
Due in one year or less	$ 44,792
Due after one year through five years	231,914
Due after five years through 10 years	73,132
Due after 10 years	6,355
Amortized cost	356,193
Available-for-sale securities, Fair value
Due in one year or less	44,909
Due after one year through five years	231,938
Due after five years through 10 years	73,020
Due after 10 years	6,391
Fair value	$ 356,258	315,822
Available-for-sale securities, Average yield
Due in one year or less	4.14%
Due after one year through five years	3.96%
Due after five years through 10 years	4.10%
Due after 10 years	4.49%
Average yield	4.02%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 10,173
Due after one year through five years	118,798
Due after five years through 10 years	12,233
Due after 10 years	0
Amortized cost	141,204
Total held-to-maturity securities, Fair value
Due in one year or less	10,084
Due after one year through five years	113,129
Due after five years through 10 years	11,198
Due after 10 years	0
Fair value	$ 134,411	126,447
Total held-to-maturity securities, Average yield
Due in one year or less	2.71%
Due after one year through five years	2.62%
Due after five years through 10 years	2.10%
Due after 10 years	0.00%
Average yield	2.58%
Obligations of U.S. states and municipalities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	20
Due after five years through 10 years	138
Due after 10 years	19,806
Amortized cost	19,964
Available-for-sale securities, Fair value
Due in one year or less	0
Due after one year through five years	20
Due after five years through 10 years	132
Due after 10 years	18,828
Fair value	$ 18,980	20,240
Available-for-sale securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	4.03%
Due after five years through 10 years	3.94%
Due after 10 years	5.13%
Average yield	5.13%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	53
Due after five years through 10 years	296
Due after 10 years	7,922
Amortized cost	8,271
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	49
Due after five years through 10 years	275
Due after 10 years	7,303
Fair value	$ 7,627	8,008
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	4.84%
Due after five years through 10 years	3.24%
Due after 10 years	4.05%
Average yield	4.02%
Non-U.S. government debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 15,489
Due after one year through five years	26,118
Due after five years through 10 years	10,948
Due after 10 years	1,232
Amortized cost	53,787
Available-for-sale securities, Fair value
Due in one year or less	15,485
Due after one year through five years	25,823
Due after five years through 10 years	10,723
Due after 10 years	1,180
Fair value	$ 53,211	45,655
Available-for-sale securities, Average yield
Due in one year or less	3.65%
Due after one year through five years	4.01%
Due after five years through 10 years	3.55%
Due after 10 years	2.68%
Average yield	3.78%
Corporate debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 7
Due after one year through five years	130
Due after five years through 10 years	0
Due after 10 years	0
Amortized cost	137
Available-for-sale securities, Fair value
Due in one year or less	2
Due after one year through five years	122
Due after five years through 10 years	0
Due after 10 years	0
Fair value	$ 124	$ 128
Available-for-sale securities, Average yield
Due in one year or less	17.50%
Due after one year through five years	15.73%
Due after five years through 10 years	0.00%
Due after 10 years	0.00%
Average yield	15.82%
Asset-backed securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 2
Due after one year through five years	283
Due after five years through 10 years	1,261
Due after 10 years	22,219
Amortized cost	23,765
Available-for-sale securities, Fair value
Due in one year or less	2
Due after one year through five years	284
Due after five years through 10 years	1,265
Due after 10 years	22,230
Fair value	$ 23,781
Available-for-sale securities, Average yield
Due in one year or less	4.98%
Due after one year through five years	5.36%
Due after five years through 10 years	5.74%
Due after 10 years	4.85%
Average yield	4.90%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	357
Due after five years through 10 years	10,140
Due after 10 years	11,701
Amortized cost	22,198
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	355
Due after five years through 10 years	10,135
Due after 10 years	11,679
Fair value	$ 22,169
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	2.78%
Due after five years through 10 years	4.40%
Due after 10 years	4.50%
Average yield	4.43%