Fair Value - Level 3 Valuation - Nonrecurring (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	$ 4,892	$ 3,744
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	319	258
Mortgage loans held for investment, net of allowance for loan losses	130,751	127,763
Total nonrecurring assets at fair value	131,689	128,690
Nonrecurring | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	2,481	2,497
Nonrecurring | Significant Unobservable Inputs (Level 3) | Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	189	113
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	497	368
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Internal Model
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	270	267
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Accepted Offer and Appraisal
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	192	74
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Internal Model and Walk Forward
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	305	294
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	1,448	1,471
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily | Internal Model
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	90	172
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily | Appraisal
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	172	448
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily | Broker Price Opinion
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	1,186	851
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily | Broker Price Opinion and Appraisal
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	$ 77	$ 278