Investment Securities - Amortized Cost and Estimated Fair Value by Contractual Maturity (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Available-for-sale securities, Amortized cost
Due in one year or less	$ 41,642
Due after one year through five years	238,802
Due after five years through 10 years	71,284
Due after 10 years	139,435
Amortized cost	491,163
Available-for-sale securities, Fair value
Due in one year or less	41,642
Due after one year through five years	240,311
Due after five years through 10 years	71,492
Due after 10 years	137,054
Fair value	$ 490,499	$ 406,852
Available-for-sale securities, Average yield
Due in one year or less	4.16%
Due after one year through five years	4.30%
Due after five years through 10 years	4.37%
Due after 10 years	4.85%
Average yield	4.46%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 30,969
Due after one year through five years	84,256
Due after five years through 10 years	66,033
Due after 10 years	112,258
Amortized cost	293,516
Total held-to-maturity securities, Fair value
Due in one year or less	30,668
Due after one year through five years	81,943
Due after five years through 10 years	60,532
Due after 10 years	101,762
Fair value	$ 274,905	247,900
Total held-to-maturity securities, Average yield
Due in one year or less	0.75%
Due after one year through five years	3.00%
Due after five years through 10 years	2.33%
Due after 10 years	3.24%
Average yield	2.70%
Supplemental information
Available for sale securities allowance for credit losses	$ 35
Unallocated portfolio layer fair value hedge basis adjustments	1,200
Held-to-maturity securities allowance for credit losses	$ 70
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	5 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	$ 1,688
Due after one year through five years	11,105
Due after five years through 10 years	4,952
Due after 10 years	86,096
Amortized cost	103,841
Available-for-sale securities, Fair value
Due in one year or less	1,677
Due after one year through five years	11,252
Due after five years through 10 years	5,012
Due after 10 years	84,452
Fair value	$ 102,393	100,769
Available-for-sale securities, Average yield
Due in one year or less	3.18%
Due after one year through five years	4.74%
Due after five years through 10 years	4.93%
Due after 10 years	4.68%
Average yield	4.68%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 894
Due after one year through five years	8,305
Due after five years through 10 years	6,315
Due after 10 years	90,686
Amortized cost	106,200
Total held-to-maturity securities, Fair value
Due in one year or less	879
Due after one year through five years	7,878
Due after five years through 10 years	5,767
Due after 10 years	80,877
Fair value	$ 95,401	99,809
Total held-to-maturity securities, Average yield
Due in one year or less	1.54%
Due after one year through five years	2.57%
Due after five years through 10 years	3.00%
Due after 10 years	2.92%
Average yield	2.89%
U.S. Treasury and government agencies
Available-for-sale securities, Amortized cost
Due in one year or less	$ 28,716
Due after one year through five years	209,735
Due after five years through 10 years	55,304
Due after 10 years	6,309
Amortized cost	300,064
Available-for-sale securities, Fair value
Due in one year or less	28,754
Due after one year through five years	211,078
Due after five years through 10 years	55,571
Due after 10 years	6,483
Fair value	$ 301,886	234,779
Available-for-sale securities, Average yield
Due in one year or less	4.38%
Due after one year through five years	4.29%
Due after five years through 10 years	4.50%
Due after 10 years	5.00%
Average yield	4.35%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 30,075
Due after one year through five years	75,721
Due after five years through 10 years	43,041
Due after 10 years	0
Amortized cost	148,837
Total held-to-maturity securities, Fair value
Due in one year or less	29,789
Due after one year through five years	73,840
Due after five years through 10 years	38,101
Due after 10 years	0
Fair value	$ 141,730	97,420
Total held-to-maturity securities, Average yield
Due in one year or less	0.72%
Due after one year through five years	3.05%
Due after five years through 10 years	1.30%
Due after 10 years	0.00%
Average yield	2.07%
Obligations of U.S. states and municipalities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 1
Due after one year through five years	11
Due after five years through 10 years	101
Due after 10 years	20,704
Amortized cost	20,817
Available-for-sale securities, Fair value
Due in one year or less	1
Due after one year through five years	11
Due after five years through 10 years	101
Due after 10 years	19,855
Fair value	$ 19,968	17,913
Available-for-sale securities, Average yield
Due in one year or less	3.47%
Due after one year through five years	3.87%
Due after five years through 10 years	4.39%
Due after 10 years	5.22%
Average yield	5.22%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	44
Due after five years through 10 years	303
Due after 10 years	8,564
Amortized cost	8,911
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	40
Due after five years through 10 years	284
Due after 10 years	7,873
Fair value	$ 8,197	8,711
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	4.64%
Due after five years through 10 years	3.30%
Due after 10 years	3.92%
Average yield	3.91%
Non-U.S. government debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 11,184
Due after one year through five years	17,483
Due after five years through 10 years	9,861
Due after 10 years	5,988
Amortized cost	44,516
Available-for-sale securities, Fair value
Due in one year or less	11,190
Due after one year through five years	17,499
Due after five years through 10 years	9,737
Due after 10 years	5,853
Fair value	$ 44,279	36,245
Available-for-sale securities, Average yield
Due in one year or less	3.67%
Due after one year through five years	4.10%
Due after five years through 10 years	3.21%
Due after 10 years	3.86%
Average yield	3.76%
Corporate debt securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 49
Due after one year through five years	108
Due after five years through 10 years	0
Due after 10 years	0
Amortized cost	157
Available-for-sale securities, Fair value
Due in one year or less	16
Due after one year through five years	109
Due after five years through 10 years	0
Due after 10 years	0
Fair value	$ 125	$ 70
Available-for-sale securities, Average yield
Due in one year or less	17.50%
Due after one year through five years	14.54%
Due after five years through 10 years	0.00%
Due after 10 years	0.00%
Average yield	15.46%
Asset-backed securities
Available-for-sale securities, Amortized cost
Due in one year or less	$ 4
Due after one year through five years	360
Due after five years through 10 years	1,066
Due after 10 years	20,338
Amortized cost	21,768
Available-for-sale securities, Fair value
Due in one year or less	4
Due after one year through five years	362
Due after five years through 10 years	1,071
Due after 10 years	20,411
Fair value	$ 21,848
Available-for-sale securities, Average yield
Due in one year or less	5.30%
Due after one year through five years	5.76%
Due after five years through 10 years	5.82%
Due after 10 years	5.42%
Average yield	5.45%
Total held-to-maturity securities, Amortized cost
Due in one year or less	$ 0
Due after one year through five years	186
Due after five years through 10 years	16,374
Due after 10 years	13,008
Amortized cost	29,568
Total held-to-maturity securities, Fair value
Due in one year or less	0
Due after one year through five years	185
Due after five years through 10 years	16,380
Due after 10 years	13,012
Fair value	$ 29,577
Total held-to-maturity securities, Average yield
Due in one year or less	0.00%
Due after one year through five years	3.82%
Due after five years through 10 years	4.78%
Due after 10 years	4.99%
Average yield	4.87%