Summary of Significant Accounting Policies - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
Weighted average number of contingently issuable shares (shares)	4,700	4,700	4,700	4,700
Incremental common shares attributable to dilutive effect of conversion of preferred stock (in shares)	26	26	26	26
Investment in securities, trading, at fair value	$ 63,156		$ 63,156		$ 69,514
Securities received as collateral	33,800		33,800		45,600
Fair value of securities received as collateral that can be resold or repledged	32,800		32,800		43,400
Acquired property	2,800		2,800		1,900
Non-mortgage-related securities
Debt and Equity Securities, FV-NI [Line Items]
Investment in securities, trading, at fair value	40,087		40,087		55,223
Non-mortgage-related securities | Pledged as collateral
Debt and Equity Securities, FV-NI [Line Items]
Investment in securities, trading, at fair value	$ 9,700		$ 9,700		$ 8,200