Residential Loans - Quarterly Activity of Residential Loans Held-for-Investment (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Transfers from loans held-for-sale to loans held-for-investment			$ 770,754	$ 1,361,015
Held-for-investment at fair value \| Sequoia Choice
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Net market valuation gain (loss)	$ (5,175)	$ (11,029)	(21,727)	4,841
Held-for-investment at fair value \| Freddie Mac SLST
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Net market valuation gain (loss)	159,687	39,783	15,254	94,788
Held-for-investment at fair value \| Legacy Sequoia
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Net market valuation gain (loss)	21,938	(103)	(38,996)	5,271
Held-for-investment at fair value \| Sequoia Choice
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Transfers from loans held-for-sale to loans held-for-investment	0	727,088	270,506	1,076,671
Held-for-investment at fair value \| Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Principal balance of loans acquired	0	0	0	39,194
Principal balance of loans sold	0	0	0	0
Transfers from loans held-for-sale to loans held-for-investment	0	0	13,258	68,703
Transfers from loans held-for-investment to loans held-for-sale	0	0	1,870,986	22,814
Net market valuation gains (losses) recorded	$ 218	$ 7,667	$ (93,314)	$ 71,323

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Principal Balance of Loans Sold During Period

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Amount of financing receivable reclassified to held-for-sale.

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Amount of increase (decrease) in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

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