Equity - Basic and Diluted Earnings Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income attributable to Redwood	$ 49,143	$ 34,310	$ 31,266	$ 54,464	$ (913)	$ 40,921	$ 32,747	$ 46,845	$ 169,183	$ 119,600	$ 140,406
Less: Dividends and undistributed earnings allocated to participating securities									(4,797)	(3,754)	(3,632)
Net income allocated to common shareholders									$ 164,386	$ 115,846	$ 136,774
Basic weighted average common shares outstanding (in shares)									101,120,744	78,724,912	76,792,957
Basic earnings per common share (in dollars per share)	$ 0.42	$ 0.33	$ 0.31	$ 0.57	$ (0.02)	$ 0.49	$ 0.42	$ 0.60	$ 1.63	$ 1.47	$ 1.78
Less: Dividends and undistributed earnings allocated to participating securities									$ (5,273)	$ (4,283)	$ (3,836)
Add back: Interest expense on convertible notes for the period, net of tax									36,212	32,653	26,898
Net income allocated to common shareholders									$ 200,122	$ 147,970	$ 163,468
Weighted average common shares outstanding (in shares)									101,147,225	78,724,912	76,792,957
Net effect of dilutive equity awards (in shares)									251,100	189,120	185,383
Net effect of assumed convertible notes conversion to common shares (in shares)									35,382,269	31,113,738	24,996,668
Diluted weighted average common shares outstanding (in shares)									136,780,594	110,027,770	101,975,008
Diluted earnings per common share (in dollars per share)	$ 0.38	$ 0.31	$ 0.30	$ 0.49	$ (0.02)	$ 0.42	$ 0.38	$ 0.50	$ 1.46	$ 1.34	$ 1.60