Fair Value - Valuation Inputs (Details)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	$ 564,000,000	$ 696,000,000
Net derivatives	157,000,000	172,000,000
Mortgage loans	3,315,000,000	3,645,000,000
Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	52,552,000,000	50,129,000,000
Total Fair Value	564,000,000	696,000,000
Total nonrecurring assets at fair value	56,633,000,000	54,645,000,000
Mortgage loans	3,315,000,000	3,645,000,000
Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26,000,000	47,000,000
Total Fair Value	514,000,000	634,000,000
Total nonrecurring assets at fair value	133,003,000,000	174,762,000,000
Mortgage loans held for sale, at lower of cost or fair value	2,196,000,000	2,029,000,000
Mortgage loans	130,022,000,000	171,857,000,000
Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26,000,000	47,000,000
Total Fair Value	514,000,000	634,000,000
Net derivatives	77,000,000	(37,000,000)
Total nonrecurring assets at fair value	1,107,000,000	1,253,000,000
Mortgage loans	477,000,000	543,000,000
Significant Unobservable Inputs (Level 3) | Recurring | Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Net derivatives	32,000,000	(62,000,000)
Significant Unobservable Inputs (Level 3) | Recurring | Dealer Mark
Fair Value Inputs, Quantitative Information [Line Items]
Net derivatives	45,000,000	25,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	3,993,000,000	4,462,000,000
Mortgage loans held for sale, at lower of cost or fair value	1,994,000,000	1,663,000,000
Other liabilities, fair value	0	0
Significant Unobservable Inputs (Level 3) | Nonrecurring | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	390,000,000	400,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans	1,020,000,000	644,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Various | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	19,000,000	12,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Various | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	182,000,000	119,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	1,994,000,000	1,571,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	0	92,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Internal Model | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans	407,000,000	1,636,000,000
Acquired property, net	230,000,000	215,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Internal Model | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans	218,000,000	27,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Appraisal | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	43,000,000	65,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Appraisal | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans	33,000,000	3,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Broker Price Opinion | Multifamily
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans	769,000,000	614,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Accepted Offer | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	23,000,000	17,000,000
Significant Unobservable Inputs (Level 3) | Nonrecurring | Walk Forward | Single-Family
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	75,000,000	91,000,000
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	47,764,000,000	46,898,000,000
Total Fair Value	0	0
Total nonrecurring assets at fair value	81,745,000,000	79,889,000,000
Mortgage loans held for sale, at lower of cost or fair value	0	0
Mortgage loans	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	47,764,000,000	46,898,000,000
Total Fair Value	0	0
Total nonrecurring assets at fair value	47,764,000,000	46,898,000,000
Mortgage loans	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Nonrecurring
Fair Value Inputs, Quantitative Information [Line Items]
Total nonrecurring assets at fair value	0	0
Significant Other Observable Inputs (Level 2)
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	4,762,000,000	3,184,000,000
Total Fair Value	50,000,000	62,000,000
Total nonrecurring assets at fair value	3,643,669,000,000	3,512,490,000,000
Mortgage loans held for sale, at lower of cost or fair value	93,000,000	48,000,000
Mortgage loans	3,571,555,000,000	3,437,979,000,000
Significant Other Observable Inputs (Level 2) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	4,762,000,000	3,184,000,000
Total Fair Value	50,000,000	62,000,000
Total nonrecurring assets at fair value	8,045,000,000	6,648,000,000
Mortgage loans	2,838,000,000	3,102,000,000
Significant Other Observable Inputs (Level 2) | Nonrecurring
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	42,000,000	30,000,000
Other liabilities, fair value	0	0
Mortgage-related | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	4,770,000,000	3,211,000,000
Mortgage-related | Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26,000,000	47,000,000
Mortgage-related | Significant Unobservable Inputs (Level 3) | Recurring | Various
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	26,000,000	47,000,000
Mortgage-related | Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	0	0
Mortgage-related | Significant Other Observable Inputs (Level 2) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	4,744,000,000	3,164,000,000
Agency | Significant Unobservable Inputs (Level 3) | Recurring | Consensus
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	331,000,000	371,000,000
Other | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	187,000,000	270,000,000
Other | Significant Unobservable Inputs (Level 3) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	183,000,000	263,000,000
Other | Significant Unobservable Inputs (Level 3) | Recurring | Various
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	100,000,000	25,000,000
Other | Significant Unobservable Inputs (Level 3) | Recurring | Discounted Cash Flow
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	$ 74,000,000	$ 142,000,000
Other | Significant Unobservable Inputs (Level 3) | Recurring | Discounted Cash Flow | Minimum | Default rate
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input	0.05300	0.05310
Other | Significant Unobservable Inputs (Level 3) | Recurring | Discounted Cash Flow | Maximum | Default rate
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input	0.05600	0.05820
Other | Significant Unobservable Inputs (Level 3) | Recurring | Discounted Cash Flow | Weighted average | Default rate
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input	0.05448	0.05577
Other | Significant Unobservable Inputs (Level 3) | Recurring | Single Vendor
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	$ 9,000,000	$ 96,000,000
Other | Significant Unobservable Inputs (Level 3) | Recurring | Single Vendor | Minimum
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input
Other | Significant Unobservable Inputs (Level 3) | Recurring | Single Vendor | Maximum
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input
Other | Significant Unobservable Inputs (Level 3) | Recurring | Single Vendor | Weighted average
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale, measurement input
Other | Quoted Prices in Active Markets for Identical Assets (Level 1) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	0	$ 0
Other | Significant Other Observable Inputs (Level 2) | Recurring
Fair Value Inputs, Quantitative Information [Line Items]
Total Fair Value	$ 4,000,000	$ 7,000,000