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Derivative financial instruments - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jun. 30, 2026 | Jun. 30, 2025 | Jun. 30, 2026 | Jun. 30, 2025 | Mar. 31, 2026 | Dec. 31, 2025 | Mar. 31, 2025 | Dec. 31, 2024
Derivative [Line Items] |  |  |  |  |  |  |  |
Notional Amount | $ 32,300 |  | $ 32,300 |  |  | $ 31,000 |  |
Cash Flow Hedges |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Equity, attributable to parent, before tax | (68) | $ 85 | (68) | $ 85 | $ 9 | 90 | $ 9 | $ (135)
Clearinghouse Credit Facilities |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Amount of initial margin posted | 161 |  | 161 |  |  | 224 |  |
Income Statement Location: us-gaap:InterestExpenseOperating |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Change in cash flow hedges derivative instruments, fair value net | 8 | (33) | 13 | (86) |  |  |  |
Interest Rate Contracts | Designated as Hedging Instrument | Fair value hedges: |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Notional Amount | 1,400 |  | 1,400 |  |  | 1,600 |  |
Interest Rate Contracts | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Notional Amount | 48,500 |  | 48,500 |  |  | 43,000 |  |
Foreign exchange and other option and futures contracts | Not Designated as Hedging Instrument |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Notional Amount | 2,400 |  | 2,400 |  |  | $ 2,400 |  |
Interest rate swap agreements |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Cash flow hedge reclassification before tax | $ 5 | $ (44) | 6 | $ (106) |  |  |  |
Interest rate swap agreements | Maturity Period 2026 |  |  |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |  |  |
Cash flow hedge loss to be reclassified within 12 months |  |  | $ 39 |  |  |  |  |

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- Definition The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480870/815-30-50-1 + Details
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- Definition The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 185 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480401/815-10-55-185 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4H -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4H + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 5A -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-5A Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 505 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481112/505-10-50-18 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 815 -SubTopic 20 -Name Accounting Standards Codification -Section 25 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org/1943274/2147480682/815-20-25-6A + Details
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- Definition Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 182 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480401/815-10-55-182 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4C -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4C Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-11 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 15 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482790/220-10-45-15 + Details
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