Equity - Basic and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Equity [Abstract]
Net income attributable to Redwood	$ 27,064	$ 16,017	$ 41,865	$ 28,350
Less: Dividends and undistributed earnings allocated to participating securities	(642)	(537)	(1,375)	(1,239)
Net income allocated to common shareholders	$ 26,422	$ 15,480	$ 40,490	$ 27,111
Basic weighted average common shares outstanding (shares)	83,936,844	82,740,012	83,650,170	82,575,636
Basic earnings per common share (usd per share)	$ 0.31	$ 0.19	$ 0.48	$ 0.33
Less: Dividends and undistributed earnings allocated to participating securities	$ (619)	$ (537)	$ (1,375)	$ (1,239)
Add back: Interest expense on convertible notes for the period, net of tax	2,789	0	0	0
Net income allocated to common shareholders	$ 29,234	$ 15,480	$ 40,490	$ 27,111
Net effect of dilutive equity awards (in shares)	1,546,038	2,292,986	1,823,735	2,418,685
Net effect of assumed convertible notes conversion to common shares (in shares)	9,466,859	0	0	0
Diluted weighted average common shares outstanding (shares)	94,949,741	85,032,998	85,473,905	84,994,321
Diluted earnings per common share (usd per share)	$ 0.31	$ 0.18	$ 0.47	$ 0.32