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Fair value measurements - Additional Information (Detail) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2025 | Mar. 31, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024 | Dec. 31, 2024
Level 3 |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves | $ 115,000,000 |  | $ 93,000,000 | $ 157,000,000 | $ 221,000,000 |
Level 3 | Residential Mortgage Loans |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Capitalized servicing rights, valuation allowance |  | $ 0 |  | 0 | 0 |
Nonrecurring |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Loans measured at fair value on nonrecurring basis | 644,000,000 |  | 1,000,000,000.0 | 644,000,000 | 1,000,000,000.0 | $ 847,000,000
Nonrecurring | Level 2 |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Loans measured at fair value on nonrecurring basis | 166,000,000 |  | 248,000,000 | 166,000,000 | 248,000,000 | 187,000,000
Nonrecurring | Level 3 |  |  |  |  |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |  |  |  |  |
Loans measured at fair value on nonrecurring basis | $ 478,000,000 |  | $ 783,000,000 | $ 478,000,000 | $ 783,000,000 | $ 660,000,000

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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/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 100 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-100 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-3 + Details
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- Definition Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Name Accounting Standards Codification -Section 55 -Paragraph 10 -SubTopic 10 -Topic 825 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482881/825-10-55-10 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 28 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-28 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 12 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482881/825-10-55-12 + Details
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