Fair Value Option - Aggregate Differences (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Long-term beneficial interests
Performing loans, ninety days or more past due	$ 0	$ 0
Lending-related commitments, fair value option elected
Long-term beneficial interests
Contractual amount of lending-related commitments	11,400,000,000	9,700,000,000
Contractual lending-related commitments, fair value	93,000,000	97,000,000
Contractual principal outstanding
Loans
Nonaccrual loans	3,795,000,000	3,825,000,000
All other performing loans	49,882,000,000	48,495,000,000
Total loans	53,732,000,000	52,385,000,000
Contractual principal outstanding | Principal-protected debt
Long-term debt
Total long-term debt	52,199,000,000	47,768,000,000
Contractual principal outstanding | Loans reported as trading assets
Loans
Nonaccrual loans	2,684,000,000	2,987,000,000
All other performing loans	10,284,000,000	9,547,000,000
Contractual principal outstanding | Loans
Loans
Nonaccrual loans	1,111,000,000	838,000,000
90 or more days past due and government guaranteed	55,000,000	65,000,000
All other performing loans	39,598,000,000	38,948,000,000
Fair value
Loans
Nonaccrual loans	1,387,000,000	1,320,000,000
All other performing loans	46,936,000,000	46,028,000,000
Total loans	48,373,000,000	47,407,000,000
Long-term debt
Total long-term debt	92,730,000,000	87,924,000,000
Long-term beneficial interests
Total long-term beneficial interests	1,000,000	1,000,000
Fair value | Principal-protected debt
Long-term debt
Total long-term debt	43,532,000,000	38,882,000,000
Fair value | Nonprincipal-protected debt
Long-term debt
Total long-term debt	49,198,000,000	49,042,000,000
Long-term beneficial interests
Total long-term beneficial interests	1,000,000	1,000,000
Fair value | Loans reported as trading assets
Loans
Nonaccrual loans	447,000,000	588,000,000
All other performing loans	8,880,000,000	7,968,000,000
Fair value | Loans
Loans
Nonaccrual loans	940,000,000	732,000,000
90 or more days past due and government guaranteed	50,000,000	59,000,000
All other performing loans	38,056,000,000	38,060,000,000
Fair value over/(under) contractual principal outstanding
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(2,408,000,000)	(2,505,000,000)
All other performing loans	(2,946,000,000)	(2,467,000,000)
Total loans	(5,359,000,000)	(4,978,000,000)
Fair value over/(under) contractual principal outstanding | Principal-protected debt
Long-term debt
Long-term debt, Fair value over/(under) contractual principal outstanding	(8,667,000,000)	(8,886,000,000)
Fair value over/(under) contractual principal outstanding | Loans reported as trading assets
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(2,237,000,000)	(2,399,000,000)
All other performing loans	(1,404,000,000)	(1,579,000,000)
Fair value over/(under) contractual principal outstanding | Loans
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(171,000,000)	(106,000,000)
90 or more days past due and government guaranteed, Fair value over/(under) contractual principal outstanding	(5,000,000)	(6,000,000)
All other performing loans	$ (1,542,000,000)	$ (888,000,000)