Fair Value - Level 3 Valuation Inputs (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	$ 37,567	$ 375
Net derivatives	451	133
Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	63,156	69,514
Available-for-sale securities	37,567	375
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	22	27
Available-for-sale securities	301	341
Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	22	27
Available-for-sale securities	301	341
Significant Unobservable Inputs (Level 3) | Recurring | Dealer Mark and Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Net derivatives	35	65
Mortgage-related securities | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	23,069	14,291
Available-for-sale securities	570	375
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	22	27
Available-for-sale securities	301	341
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring | Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	22	27
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring | Primarily Consensus and Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	$ 301
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring | Primarily Consensus, Single Vendor, and Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities		$ 341