Fair Value - Valuation Inputs (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value Inputs, Quantitative Information [Line Items]
Total available-for-sale securities	$ 469	$ 564
Net derivatives	151	157
Total multifamily mortgage loans held for investment, at amortized cost	3,744	3,315
Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	78,728	52,552
Total available-for-sale securities	469	564
Total multifamily mortgage loans held for investment, at amortized cost	3,744	3,315
Total nonrecurring assets at fair value	83,120	56,633
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	28	26
Total available-for-sale securities	427	514
Total mortgage loans held for sale, at lower of cost or fair value	258	2,196
Total multifamily mortgage loans held for investment, at amortized cost	127,763	130,022
Total nonrecurring assets at fair value	128,690	133,003
Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	28	26
Total available-for-sale securities	427	514
Total multifamily mortgage loans held for investment, at amortized cost	399	477
Total nonrecurring assets at fair value	908	1,107
Significant Unobservable Inputs (Level 3) | Recurring | Dealer Mark and Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Net derivatives	39	77
Significant Unobservable Inputs (Level 3) | Nonrecurring
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	2,497	3,993
Significant Unobservable Inputs (Level 3) | Nonrecurring | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net:	368	390
Significant Unobservable Inputs (Level 3) | Nonrecurring | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Total multifamily mortgage loans held for investment, at amortized cost	1,471	1,020
Significant Unobservable Inputs (Level 3) | Nonrecurring | Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Total mortgage loans held for sale, at lower of cost or fair value	113	1,994
Significant Unobservable Inputs (Level 3) | Nonrecurring | Internal Model | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Total multifamily mortgage loans held for investment, at amortized cost	267	407
Significant Unobservable Inputs (Level 3) | Nonrecurring | Internal Model | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Total multifamily mortgage loans held for investment, at amortized cost	172	218
Significant Unobservable Inputs (Level 3) | Nonrecurring | Appraisal | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Total multifamily mortgage loans held for investment, at amortized cost	448	33
Significant Unobservable Inputs (Level 3) | Nonrecurring | Broker Price Opinion | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Total multifamily mortgage loans held for investment, at amortized cost	851	769
Acquired property, net:	278	182
Significant Unobservable Inputs (Level 3) | Nonrecurring | Accepted Offer and Appraisal | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net:	74	66
Significant Unobservable Inputs (Level 3) | Nonrecurring | Internal Model and Walk Forward | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net:	294	324
Mortgage-related securities | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	1,098	4,770
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	28	26
Mortgage-related securities | Significant Unobservable Inputs (Level 3) | Recurring | Primarily Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	28	26
Agency | Significant Unobservable Inputs (Level 3) | Recurring | Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Total available-for-sale securities	301	331
Other | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total available-for-sale securities	130	187
Other | Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total available-for-sale securities	126	183
Other | Significant Unobservable Inputs (Level 3) | Recurring | Primarily Discounted Cash Flow, Single Vendor, and Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Total available-for-sale securities	$ 126	$ 183