Principles of Consolidation - Summary of Unconsolidated Variable Interest Entity's Sponsored by Redwood (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
On-balance sheet assets, at fair value:
Available-for-sale securities	$ 129,243	$ 239,334
Servicing asset, fair value	282,743	151,582
Mortgage servicing rights
On-balance sheet assets, at fair value:
Servicing asset, fair value	23,616	42,224	$ 55,284	$ 60,281
Variable Interest Entity, Not Primary Beneficiary
On-balance sheet assets, at fair value:
Maximum loss exposure	154,809	269,328
Assets transferred:
Principal balance of loans outstanding	11,181,034	10,299,442
Principal balance of loans 30 days delinquent	40,930	41,809
Variable Interest Entity, Not Primary Beneficiary | Interest-only, senior and subordinate securities, classified as trading
On-balance sheet assets, at fair value:
Interest-only, senior and subordinate securities, classified as trading	54,894	88,425
Variable Interest Entity, Not Primary Beneficiary | Subordinate securities, classified as AFS
On-balance sheet assets, at fair value:
Available-for-sale securities	77,433	140,649
Variable Interest Entity, Not Primary Beneficiary | Mortgage servicing rights
On-balance sheet assets, at fair value:
Servicing asset, fair value	$ 22,482	$ 40,254