Real Estate Securities - Components of Carrying Value (Which Equals Fair Value) of Residential Available for Sale Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	$ 698,356	$ 829,245
Senior Securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	140,616	279,251
Senior Securities \| Prime
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	111,523	210,993
Senior Securities \| Non-prime
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	29,093	68,258
Re-REMIC
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	162,970	165,064
Subordinate Securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	394,770	384,930
Subordinate Securities \| Non-prime
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	1,000	1,000
Residential
Schedule of Available-for-sale Securities [Line Items]
Principal balance	845,732	973,227
Credit reserve	(48,547)	(48,869)
Unamortized discount, net	(219,630)	(237,107)
Amortized cost	577,555	687,251
Gross unrealized gains	127,014	147,001
Gross unrealized losses	(6,213)	(5,007)
Carrying Value	698,356	829,245
Residential \| Senior Securities \| Prime
Schedule of Available-for-sale Securities [Line Items]
Principal balance	120,577	217,605
Credit reserve	(1,108)	(1,305)
Unamortized discount, net	(13,491)	(22,079)
Amortized cost	105,978	194,221
Gross unrealized gains	9,326	20,263
Gross unrealized losses	(3,781)	(3,491)
Carrying Value	111,523	210,993
Residential \| Senior Securities \| Non-prime
Schedule of Available-for-sale Securities [Line Items]
Principal balance	31,781	75,591
Credit reserve	(687)	(5,101)
Unamortized discount, net	(3,262)	(8,395)
Amortized cost	27,832	62,095
Gross unrealized gains	1,482	6,249
Gross unrealized losses	(221)	(86)
Carrying Value	29,093	68,258
Residential \| Re-REMIC
Schedule of Available-for-sale Securities [Line Items]
Principal balance	189,146	189,782
Credit reserve	(11,258)	(10,332)
Unamortized discount, net	(66,586)	(71,670)
Amortized cost	111,302	107,780
Gross unrealized gains	51,668	57,284
Gross unrealized losses	0	0
Carrying Value	162,970	165,064
Residential \| Subordinate Securities
Schedule of Available-for-sale Securities [Line Items]
Principal balance	504,228	490,249
Credit reserve	(35,494)	(32,131)
Unamortized discount, net	(136,291)	(134,963)
Amortized cost	332,443	323,155
Gross unrealized gains	64,538	63,205
Gross unrealized losses	(2,211)	(1,430)
Carrying Value	$ 394,770	$ 384,930

Balance of credit reserve on available-for-sale securities.

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Available For Sale Securities Principal Balance

+ References

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- Definition

Balance of net unamortized discount on available-for-sale securities.

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: 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=51813488&loc=d3e22054-111558

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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