Fair Value of Assets and Liabilities - Fair Value Reconciliation (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Senior asset-backed securities related to Structured Program transactions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning	$ 0		$ 0
Originations and purchases, and additions	144,680		144,680
Principal payments and cash received	(1,290)		(1,290)
Interest income accretion and fair value adjustments recorded in earnings, and change in unrealized gain (loss)	(605)		(605)
Ending	142,785		142,785
Other asset-backed securities related to Structured Program transactions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning	10,397		12,469
Originations and purchases, and additions	8,667		8,780
Principal payments and cash received	(2,084)		(4,269)
Ending	16,980		16,980
Loans Held For Sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning	44,647	$ 156,730	110,400	$ 142,370
Originations and purchases, and additions	1,272,118	2,728,499	2,477,147	4,999,424
Sales	(1,238,252)	(2,811,843)	(2,485,498)	(5,069,544)
Principal payments and cash received	(5,135)	(8,524)	(11,600)	(21,860)
Transfers	191,807	(11,888)	191,807	(11,888)
Interest income accretion and fair value adjustments recorded in earnings, and change in unrealized gain (loss)	(14,824)	9,837	(31,895)	24,309
Ending	250,361	62,811	250,361	62,811
Loans Held for Investment
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning	748,618	15,384	925,938	21,240
Originations and purchases, and additions	0	0	4,037	14
Principal payments and cash received	(156,287)	(5,724)	(342,738)	(11,747)
Transfers	(191,634)	11,966	(191,634)	11,966
Interest income accretion and fair value adjustments recorded in earnings, and change in unrealized gain (loss)	3,422	(1,043)	8,516	(890)
Ending	$ 404,119	$ 20,583	$ 404,119	$ 20,583

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers In (Out) Adjustment

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-SubTopic 10
-Topic 820
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

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