Business Purpose Loans - Activity and Characteristics of Business Purpose Loans (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2022 USD ($) loan	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Purchases of held-for-sale loans	$ 2,197,570	$ 3,150,432
Principal balance of loans sold to third parties	23,050	11,746
Transfers from loans held-for-sale to loans held-for-investment	1,098,459	301,298
Single-family rental loans, held-for-sale \| Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Purchases of held-for-sale loans	442,727	253,098
Principal balance of loans acquired	61,892	0
Principal balance of loans sold to third parties	331,502	0
Transfers from loans held-for-sale to loans held-for-investment	0	169,404
Gain (loss) on investments	0	0
Fair value of loans	505,889		$ 358,309
Single-family rental loans, held-for-sale \| Redwood \| Business Purpose Mortgage Banking Activities, Net:
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	(24,468)	10,248
Bridge loans held-for-investment
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Purchases of held-for-sale loans	411,938	133,229
Principal balance of loans acquired	2,983	0
Principal balance of loans sold to third parties	0	8,877
Gain (loss) on investments	(759)	3,304
Fair value of loans	917,979		666,364
Bridge loans held-for-investment \| Business Purpose Mortgage Banking Activities, Net:
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	2,375	542
Bridge loans held-for-investment \| Redwood
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	0
Business Purpose Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fee income	14,000	6,000
Fair value of loans	4,754,778		4,790,989
Single Family Rental Loans Held For Investment At Fair Value \| Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fair value of loans	0		$ 0
Single Family Rental Loans Held For Investment At Fair Value \| CAFL
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	$ (191,903)	(60,901)
Number of loans \| loan	1,116		1,173
Unpaid principal balance	$ 3,083,716		$ 3,340,949
Fair value of loans	$ 3,038,939		$ 3,488,074
Weighted average coupon rate (as a percent)	5.15%		5.17%
Contract maturities	6 years		6 years
Fair value of loans with 90+ day delinquencies	$ 12,623		$ 12,648
Number of loans in foreclosure \| loan	9		9
Single Family Rental Loans Held For Investment At Fair Value \| CAFL \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans with 90+ day delinquencies \| loan	22		18
Fair value of loans with 90+ day delinquencies	$ 52,725		$ 41,998
Bridge Loans Held For Investment At Fair Value \| CAFL
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	$ (1,384)	$ 0
Single-Family Rental Loans, Held-For-Sale \| Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	239		245
Unpaid principal balance	$ 518,230		$ 348,232
Fair value of loans	$ 505,889		$ 358,309
Weighted average coupon rate (as a percent)	4.76%		4.73%
Contract maturities	11 years		12 years
Fair value of loans with 90+ day delinquencies	$ 5,301		$ 5,473
Number of loans in foreclosure \| loan	5		7
Unpaid principal balance of loans in foreclosure	$ 4,153		$ 4,305
Single-Family Rental Loans, Held-For-Sale \| Redwood \| Loans Pledged As Collateral, Short Term Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	66,685		75,873
Single-Family Rental Loans, Held-For-Sale \| Redwood \| Loans Pledged As Collateral, Long Term debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	376,502		244,703
Single-Family Rental Loans, Held-For-Sale \| Redwood \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fair value of loans	$ 4,086		$ 4,238
Number of loans with 90+ day delinquencies \| loan	4		6
Fair value of loans with 90+ day delinquencies	$ 5,212		$ 5,384
Business Purpose Bridge Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	1,384		1,134
Unpaid principal balance	$ 921,208		$ 670,392
Fair value of loans	$ 917,979		$ 666,364
Weighted average coupon rate (as a percent)	6.38%		6.91%
Contract maturities	1 year		1 year
Fair value of loans with 90+ day delinquencies	$ 42,152		$ 18,043
Number of loans in foreclosure \| loan	37		28
Unpaid principal balance of loans in foreclosure	$ 37,641		$ 14,257
Business Purpose Bridge Loans \| Loans Pledged As Collateral, Short Term Debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	62,494		91,814
Business Purpose Bridge Loans \| Loans Pledged As Collateral, Long Term debt
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	815,580		554,597
Business Purpose Bridge Loans \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fair value of loans	$ 28,319		$ 14,218
Number of loans with 90+ day delinquencies \| loan	56		31
Fair value of loans with 90+ day delinquencies	$ 32,830		$ 18,032
Business Purpose Bridge Loans \| CAFL
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of loans \| loan	1,375		1,640
Unpaid principal balance	$ 288,823		$ 274,617
Fair value of loans	$ 291,971		$ 278,242
Weighted average coupon rate (as a percent)	6.77%		7.05%
Contract maturities	1 year
Fair value of loans with 90+ day delinquencies	$ 4,472		$ 0
Number of loans in foreclosure \| loan	3		0
Unpaid principal balance of loans in foreclosure	$ 4,472		$ 0
Business Purpose Bridge Loans \| CAFL \| Financing Receivables, Equal to Greater than 90 Days Past Due
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fair value of loans	$ 7,847		$ 0
Number of loans with 90+ day delinquencies \| loan	48		0
Fair value of loans with 90+ day delinquencies	$ 7,847		$ 0

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Number of mortgage loans within 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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The aggregate cash outflow used to purchase all loans that are held with the intention to resell in the near future.

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