Fair Value Option - Aggregate Differences (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025
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	21,600,000,000	18,900,000,000
Contractual lending-related commitments, fair value	82,000,000	42,000,000
Contractual principal outstanding
Loans
Nonaccrual loans	5,180,000,000	5,437,000,000
All other performing loans	76,606,000,000	83,654,000,000
Total loans	81,994,000,000	89,243,000,000
Contractual principal outstanding | Principal-protected debt
Long-term debt
Total long-term debt	85,048,000,000	73,984,000,000
Contractual principal outstanding | Loans reported as trading assets
Loans
Nonaccrual loans	3,581,000,000	3,443,000,000
All other performing loans	15,177,000,000	14,852,000,000
Contractual principal outstanding | Loans
Loans
Nonaccrual loans	1,599,000,000	1,994,000,000
90 or more days past due and government guaranteed	208,000,000	152,000,000
All other performing loans	61,429,000,000	68,802,000,000
Fair value
Loans
Nonaccrual loans	1,792,000,000	2,063,000,000
All other performing loans	73,652,000,000	81,402,000,000
Total loans	75,643,000,000	83,609,000,000
Long-term debt
Total long-term debt	144,704,000,000	134,559,000,000
Long-term beneficial interests
Total long-term beneficial interests	5,000,000	5,000,000
Fair value | Principal-protected debt
Long-term debt
Total long-term debt	72,199,000,000	63,770,000,000
Fair value | Nonprincipal-protected debt
Long-term debt
Total long-term debt	72,505,000,000	70,789,000,000
Long-term beneficial interests
Total long-term beneficial interests	5,000,000	5,000,000
Fair value | Loans reported as trading assets
Loans
Nonaccrual loans	651,000,000	545,000,000
All other performing loans	12,737,000,000	12,380,000,000
Fair value | Loans
Loans
Nonaccrual loans	1,141,000,000	1,518,000,000
90 or more days past due and government guaranteed	199,000,000	144,000,000
All other performing loans	60,915,000,000	69,022,000,000
Fair value over/(under) contractual principal outstanding
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(3,388,000,000)	(3,374,000,000)
All other performing loans	(2,954,000,000)	(2,252,000,000)
Total loans	(6,351,000,000)	(5,634,000,000)
Fair value over/(under) contractual principal outstanding | Principal-protected debt
Long-term debt
Long-term debt, Fair value over/(under) contractual principal outstanding	(12,849,000,000)	(10,214,000,000)
Fair value over/(under) contractual principal outstanding | Loans reported as trading assets
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(2,930,000,000)	(2,898,000,000)
All other performing loans	(2,440,000,000)	(2,472,000,000)
Fair value over/(under) contractual principal outstanding | Loans
Loans
Nonaccrual loans, Fair value over/(under) contractual principal outstanding	(458,000,000)	(476,000,000)
90 or more days past due and government guaranteed, Fair value over/(under) contractual principal outstanding	(9,000,000)	(8,000,000)
All other performing loans	$ (514,000,000)	$ 220,000,000