Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share Disclosure [Line Items]
Basic earnings per common share	$ 0.78	$ 0.24	$ 1.50	$ 0.62
Net income attributable to Redwood	$ 65,573	$ 19,527	$ 126,183	$ 49,990
Basic weighted average common shares outstanding	82,123,823	78,815,313	81,729,014	78,606,336
Net effect of dilutive equity awards	2,222,440	0	2,274,311	0
Net effect of assumed convertible notes conversion to common shares	11,825,450		7,644,075
Diluted weighted average common shares outstanding	96,171,713	78,815,313	91,647,400	79,965,406
Diluted earnings per common share	$ 0.71	$ 0.24	$ 1.40	$ 0.61
Basic Earnings (Loss) Per Common Share
Earnings Per Share Disclosure [Line Items]
Net income attributable to Redwood	65,573	19,527	126,183	49,990
Less: Dividends and undistributed earnings allocated to participating securities	(1,830)	(538)	(3,819)	(1,491)
Net income allocated to common shareholders	63,743	18,989	122,364	48,499
Basic weighted average common shares outstanding	82,123,823	78,815,313	81,729,014	78,606,336
Diluted Earnings (Loss) Per Common Share
Earnings Per Share Disclosure [Line Items]
Net income attributable to Redwood	65,573	19,527	126,183	49,990
Less: Dividends and undistributed earnings allocated to participating securities	(1,175)	(538)	(2,527)	(1,336)
Add back: Interest expense on convertible notes	3,856		4,933
Net income allocated to common shareholders	$ 68,254	$ 18,989	$ 128,589	$ 48,654
Basic weighted average common shares outstanding	82,123,823	78,815,313	81,729,014	78,606,336
Net effect of dilutive equity awards	2,222,440		2,274,311	1,359,070
Net effect of assumed convertible notes conversion to common shares	11,825,450		7,644,075
Diluted weighted average common shares outstanding	96,171,713	78,815,313	91,647,400	79,965,406