Fair Value - Level 3 Valuation - Nonrecurring (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, net of allowance for loan losses	$ 3,433,000,000	$ 3,645,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	84,442,000,000	79,889,000,000
Mortgage loans held-for-sale, at lower of cost or fair value	0	0
Mortgage loans held for investment, net of allowance for loan losses	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	3,538,105,000,000	3,512,490,000,000
Mortgage loans held-for-sale, at lower of cost or fair value	31,000,000	48,000,000
Mortgage loans held for investment, net of allowance for loan losses	3,455,655,000,000	3,437,979,000,000
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	167,437,000,000	174,762,000,000
Mortgage loans held-for-sale, at lower of cost or fair value	495,000,000	2,029,000,000
Mortgage loans held for investment, net of allowance for loan losses	166,079,000,000	171,857,000,000
Nonrecurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	0	0
Nonrecurring | Significant Other Observable Inputs (Level 2)
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	23,000,000	30,000,000
Total nonrecurring liabilities at fair value	0	0
Nonrecurring | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	2,554,000,000	4,462,000,000
Mortgage loans held-for-sale, at lower of cost or fair value	306,000,000	1,663,000,000
Total nonrecurring liabilities at fair value	0	0
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	209,000,000	1,571,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	97,000,000	92,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	366,000,000	400,000,000
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	815,000,000	1,636,000,000
Acquired property, net	202,000,000	215,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Appraisal
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	35,000,000	65,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Accepted Offer
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	22,000,000	17,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Walk Forward
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	94,000,000	91,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Single-Family | Various
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	13,000,000	12,000,000
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	1,005,000,000	644,000,000
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	183,000,000	27,000,000
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	49,000,000	3,000,000
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	773,000,000	614,000,000
Nonrecurring | Significant Unobservable Inputs (Level 3) | Multifamily | Various
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	$ 62,000,000	$ 119,000,000