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Fair value measurements - Other information (Detail) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2024 USD ($) | Dec. 31, 2023 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Investments in equity securities | $ 335,864 | [1] | $ 353,842 | [2]
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Investments in equity securities | 10,672 |  | $ 10,474 |
Significant Unobservable Inputs (Level 3) [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Discounted Cash Flow [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Investments in equity securities | 8,609 |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Common Stock Warrants [Member] | Fair Value, Measurements, Recurring [Member] | Warrant Pricing Model [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Investments in equity securities | $ 2,058 |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Measurement Input, Expected Term | Weighted Average [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Discounted Cash Flow [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Unobservable inputs, term | 6 years |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Measurement Input, Expected Term | Weighted Average [Member] | Common Stock Warrants [Member] | Fair Value, Measurements, Recurring [Member] | Warrant Pricing Model [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Unobservable inputs, term | 6 years |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Discounts for Liquidity and Subordination [Member] | Weighted Average [Member] | Preferred Stock [Member] | Fair Value, Measurements, Recurring [Member] | Discounted Cash Flow [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Unobservable inputs | 0.0372 |  |  |
Significant Unobservable Inputs (Level 3) [Member] | Measurement Input, Option Volatility | Weighted Average [Member] | Common Stock Warrants [Member] | Fair Value, Measurements, Recurring [Member] | Warrant Pricing Model [Member] |  |  |  |
Fair Value Measurement Inputs and Valuation Techniques [Line Items] |  |  |  |
Unobservable inputs | 0.41 |  |  |
[1] | Approximately 75% of the aggregate fair value was concentrated in five companies (American Express Company – $34.5 billion; Apple Inc. – $135.4 billion; Bank of America Corporation – $39.2 billion; The Coca-Cola Company – $24.5 billion and Chevron Corporation – $19.4 billion).
[2] | Approximately 79% of the aggregate fair value was concentrated in five companies (American Express Company – $28.4 billion; Apple Inc. – $174.3 billion; Bank of America Corporation – $34.8 billion; The Coca-Cola Company – $23.6 billion and Chevron Corporation – $18.8 billion).

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