Loans Held for Investment - Narrative (Detail) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2020	Dec. 31, 2019
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Securitized debt loans held for investment at cost	$ 13,000,000,000.0	$ 13,700,000,000
Loans Held for Investment at Fair Value
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Purchases	0	1,800,000,000
Retained balance		124,000,000
Fair Value \| Seasoned Subprime Residential Mortgage Loans
Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]
Fair value of loans 90 days or more past due	$ 706,000,000	$ 597,000,000

Residential mortgage loans in the securitized loan portfolio that are 90 or more days past due.

No definition available.

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- Definition

Secured financing obligations carried at cost as of the reporting date consisting of securitizations that are collateralized by residential adjustable or fixed rate mortgage loans that have been placed in a trust and pay interest and principal to the debt holders of that securitization.

+ References

No definition available.

+ Details

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- Definition

Securitized Loans Held For Investment By Consolidated Variable Interest Entities [Line Items]

+ References

No definition available.

+ Details

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- Definition

Amortized amount of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122739-111746

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122492-111745

Reference 3: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

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- Definition

Amount of additions from purchases, assumption or transfer to contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

+ Details

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- Details

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- Details

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