Business Purpose Loans - Activity and Characteristics of Business Purpose Loans (Details) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($)
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Purchases of held-for-sale loans	$ 4,431,468	$ 5,823,547	$ 7,162,131
Principal balance of loans sold to third parties	27,210	84,303	84,495
Transfers from loans held-for-sale to loans held-for-investment	$ 1,868,656	1,801,560	2,062,809
Number of loans transferred \| loan	5
Transfers from residential loans to real estate owned	$ 14,229	$ 8,609	$ 4,104
Number of Loans \| loan	198	669
Principal amount outstanding on loans securitized	$ 172,748	$ 524,928
Commitment To Fund Residential Bridge Loan
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Other commitment	$ 216,000
Single-family rental loans, held-for-sale
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of Loans \| loan	65	201
Principal amount outstanding on loans securitized	$ 234,475	$ 321,637
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	979,696	513,725
Principal balance of loans sold to third parties	(110,836)	20,426
Transfers from loans held-for-sale to loans held-for-investment	1,292,633	717,934
Gain (loss) on investments	(20,806)	272
Loans, at fair value	245,394	331,565
Single-family rental loans, held-for-sale \| Redwood \| Business Purpose Mortgage Banking Activities
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	81,032	13,363
Single-family rental loans, held-for-sale \| CAFL
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	$ 1,290,000	$ 394,000
Number of securitization entities to which asset transferred \| loan	5	1
Single-family rental loans held-for-investment \| Redwood
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of Loans \| loan		107
Principal amount outstanding on loans securitized		$ 231,211
Loans, at fair value	$ 0	237,620
Single-family rental loans held-for-investment \| CAFL
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	$ 32,331	$ (14,681)
Number of Loans \| loan	1,094	783
Principal amount outstanding on loans securitized	$ 3,017,137	$ 2,078,214
Loans, at fair value	$ 3,249,194	$ 2,192,552
Weighted average coupon rate	5.44%	5.70%
Contract maturities	5 years	7 years
Loans held as assets, 90 days or more past due	$ 24,745	$ 9,169
Number of loans in foreclosure \| loan	10	5
Single-family rental loans held-for-investment \| 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 past due \| loan	22	18
Loans held as assets, 90 days or more past due	$ 61,440	$ 29,039
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	451,554	501,355
Principal balance of loans sold to third parties	(25,151)	56,484
Gain (loss) on investments	(10,629)	$ (2,139)
Transfers from residential loans to real estate owned	$ 6,000
Number of Loans \| loan	1,725	2,653
Principal amount outstanding on loans securitized	$ 649,532	$ 741,232
Loans, at fair value	$ 641,765	745,006
Bridge loans held-for-investment \| Minimum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Original maturity (in months)	6 months
Bridge loans held-for-investment \| Maximum
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Original maturity (in months)	24 months
Bridge loans held-for-investment \| Business Purpose Mortgage Banking Activities
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Gain (loss) on investments	$ (2,916)	3,342
Business Purpose Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Fee income	19,000	16,000
Loans, at fair value	$ 4,136,353	$ 3,506,743
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	65	308
Principal amount outstanding on loans securitized	$ 234,475	$ 552,848
Loans, at fair value	$ 245,394	$ 569,185
Weighted average coupon rate	4.84%	4.96%
Contract maturities	8 years	9 years
Loans held as assets, 90 days or more past due	$ 0	$ 130
Number of loans in foreclosure \| loan	0	1
Loans held as assets amount in foreclosure	$ 0	$ 130
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	34,098	$ 504,237
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	$ 154,774
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]
Number of loans past due \| loan	10	2
Loans held as assets, 90 days or more past due	$ 7,127	$ 1,818
Loans past due	$ 6,143	$ 1,818
Business Purpose Bridge Loans
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Number of Loans \| loan	1,725	2,653
Principal amount outstanding on loans securitized	$ 649,532	$ 742,528
Loans, at fair value	$ 641,765	$ 745,006
Weighted average coupon rate	8.09%	8.11%
Contract maturities	1 year	2 years
Loans held as assets, 90 days or more past due	$ 38,552	$ 14,186
Number of loans in foreclosure \| loan	25	31
Loans held as assets amount in foreclosure	$ 33,066	$ 12,111
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	92,931	$ 694,964
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	$ 544,151
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]
Number of loans past due \| loan	31	15
Loans held as assets, 90 days or more past due	$ 39,415	$ 8,987
Loans past due	$ 33,605	$ 6,917

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