Fair Value Level 3 Valuation - Nonrecurring (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	$ 7,701	$ 7,825
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	86	229
Mortgage loans held for investment, at fair value	3,395,898	3,270,535
Total assets at fair value	3,439,362	3,313,691
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	8,402	7,054
Mortgage loans held for investment, at fair value	118,612	127,650
Total assets at fair value	128,464	136,048
Fair Value, Nonrecurring [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	4	274
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	3,653	1,076
Total assets at fair value	6,019	2,598
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single Vendor Without Inputs [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	1,886	605
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Consensus Without Inputs [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held-for-sale, at lower of cost or fair value	$ 1,767	$ 471
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Accepted Offers [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Number of Acquired Properties Valuated, Percentage	14.00%	12.00%
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Proprietary Home Price Model and Appraisals [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Number of Acquired Properties Valuated, Percentage	81.00%	85.00%
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	$ 816	$ 918
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member] \| Various Valuation Technique without Inputs [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	52	51
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member] \| Internal Model [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	1,491	555
Acquired property, net	113	164
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member] \| Accepted Offers [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	106	101
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member] \| Appraisals [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	356	362
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Single-family [Member] \| Walk Forwards [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Acquired property, net	189	240
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Multifamily [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	52	40
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Multifamily [Member] \| Various Valuation Technique without Inputs [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	52	16
Acquired property, net	7	9
Fair Value, Nonrecurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Multifamily [Member] \| Asset Manager Estimate [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	$ 0	$ 24

The percentage of acquired property valued using different valuation techniques based on the number of properties.

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- Definition

Carrying amount as of the balance sheet date of real estate owned and foreclosed assets. Foreclosed assets include all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

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- Definition

Fair value portion of mortgage loans held-for-sale.

+ References

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