Securities by Accounting Classification, Collateral Type, and Ownership Entity (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Investment Holdings [Line Items]
Trading securities	$ 296,978	$ 329,717
Available-for-sale securities	740,623	825,119
Senior Securities \| Redwood
Investment Holdings [Line Items]
Trading securities	18,686	19,742
Available-for-sale securities	574,664	642,256
Senior Securities \| Redwood \| Residential Prime
Investment Holdings [Line Items]
Available-for-sale securities	285,946	315,891
Senior Securities \| Redwood \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	18,686	19,742
Available-for-sale securities	288,718	326,365
Re-REMIC \| Redwood
Investment Holdings [Line Items]
Available-for-sale securities	77,575	85,077
Subordinate \| Redwood
Investment Holdings [Line Items]
Trading securities	1,765	1,612
Available-for-sale securities	88,384	74,530
Subordinate \| Redwood \| Residential Prime
Investment Holdings [Line Items]
Trading securities	302	386
Available-for-sale securities	71,543	53,846
Subordinate \| Redwood \| Commercial
Investment Holdings [Line Items]
Available-for-sale securities	5,865	7,496
Subordinate \| Redwood \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	160	188
Available-for-sale securities	10,876	13,188
Subordinate \| Redwood \| CDO
Investment Holdings [Line Items]
Trading securities	1,303	1,038
Available-for-sale securities	100
Redwood
Investment Holdings [Line Items]
Trading securities	20,451	21,354
Available-for-sale securities	740,623	801,863
Acacia
Investment Holdings [Line Items]
Trading securities	276,527	308,363
Acacia \| Senior Securities
Investment Holdings [Line Items]
Trading securities	119,160	133,035
Acacia \| Senior Securities \| Residential Prime
Investment Holdings [Line Items]
Trading securities	3,645	4,412
Acacia \| Senior Securities \| Commercial
Investment Holdings [Line Items]
Trading securities	11,405	11,000
Acacia \| Senior Securities \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	104,110	117,623
Acacia \| Subordinate
Investment Holdings [Line Items]
Trading securities	157,367	175,328
Acacia \| Subordinate \| Residential Prime
Investment Holdings [Line Items]
Trading securities	40,236	49,620
Acacia \| Subordinate \| Commercial
Investment Holdings [Line Items]
Trading securities	30,869	32,828
Acacia \| Subordinate \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	65,764	76,839
Acacia \| Subordinate \| CDO
Investment Holdings [Line Items]
Trading securities	20,498	16,041
The Fund
Investment Holdings [Line Items]
Available-for-sale securities		23,256
The Fund \| Senior Securities
Investment Holdings [Line Items]
Available-for-sale securities		12,915
The Fund \| Senior Securities \| Residential non-prime
Investment Holdings [Line Items]
Available-for-sale securities		12,915
The Fund \| Subordinate
Investment Holdings [Line Items]
Available-for-sale securities		10,341
The Fund \| Subordinate \| Residential non-prime
Investment Holdings [Line Items]
Available-for-sale securities		6,096
The Fund \| Subordinate \| CDO
Investment Holdings [Line Items]
Available-for-sale securities		4,245
Senior Securities
Investment Holdings [Line Items]
Trading securities	137,846	152,777
Available-for-sale securities	574,664	655,171
Senior Securities \| Residential Prime
Investment Holdings [Line Items]
Trading securities	3,645	4,412
Available-for-sale securities	285,946	315,891
Senior Securities \| Commercial
Investment Holdings [Line Items]
Trading securities	11,405	11,000
Senior Securities \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	122,796	137,365
Available-for-sale securities	288,718	339,280
Re-REMIC
Investment Holdings [Line Items]
Available-for-sale securities	77,575	85,077
Subordinate
Investment Holdings [Line Items]
Trading securities	159,132	176,940
Available-for-sale securities	88,384	84,871
Subordinate \| Residential Prime
Investment Holdings [Line Items]
Trading securities	40,538	50,006
Available-for-sale securities	71,543	53,846
Subordinate \| Commercial
Investment Holdings [Line Items]
Trading securities	30,869	32,828
Available-for-sale securities	5,865	7,496
Subordinate \| Residential non-prime
Investment Holdings [Line Items]
Trading securities	65,924	77,027
Available-for-sale securities	10,876	19,284
Subordinate \| CDO
Investment Holdings [Line Items]
Trading securities	21,801	17,079
Available-for-sale securities	100	4,245
Commercial
Investment Holdings [Line Items]
Available-for-sale securities	5,865	7,496
CDO
Investment Holdings [Line Items]
Available-for-sale securities	$ 100	$ 4,245

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15E
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 14
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

+ Details

- Definition

The total of financial instruments that are bought and held principally for the purpose of selling them in the near term (thus held for only a short period of time) or for debt and equity securities formerly categorized as available-for-sale or held-to-maturity which the entity held as of the date it opted to account for such securities at fair value. An enterprise may also categorize such a security as trading without the intent to sell it in the near term assuming the decision to categorize the security as trading occurred at acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 29
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26626-111562

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Implementation Guide (Q and A)
-Number FAS115
-Paragraph 35
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

+ Details