Fair Value - Level 3 Valuation Inputs (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:	$ 388	$ 469
Net derivatives	113	151
Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	71,268	78,728
Available-for-sale securities:	388	469
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26	28
Available-for-sale securities:	351	427
Significant Unobservable Inputs (Level 3) \| Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26	28
Available-for-sale securities:	351	427
Significant Unobservable Inputs (Level 3) \| Recurring \| Dealer Mark and Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Net derivatives	48	39
Mortgage-related \| Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	5,102	1,098
Mortgage-related \| Significant Unobservable Inputs (Level 3) \| Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26	28
Mortgage-related \| Significant Unobservable Inputs (Level 3) \| Recurring \| Primarily Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26	28
Agency \| Significant Unobservable Inputs (Level 3) \| Recurring \| Consensus and Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:	283
Agency \| Significant Unobservable Inputs (Level 3) \| Recurring \| Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:		301
Other mortgage-related \| Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:	72	130
Other mortgage-related \| Significant Unobservable Inputs (Level 3) \| Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:	68	126
Other mortgage-related \| Significant Unobservable Inputs (Level 3) \| Recurring \| Primarily Single Vendor and Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:	$ 68
Other mortgage-related \| Significant Unobservable Inputs (Level 3) \| Recurring \| Primarily Discounted Cash Flow, Single Vendor, and Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities:		$ 126

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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