Components of Carrying Value (Which Equals Fair Value) of Residential Available for Sale Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	$ 1,267,624us-gaap_AvailableForSaleSecurities	$ 1,558,306us-gaap_AvailableForSaleSecurities
Senior Securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	487,557	855,692
Senior Securities \| Prime
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	307,813	662,306
Senior Securities \| Non-prime
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	179,744	193,386
Re-REMIC
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	168,347	176,376
Subordinate Securities
Schedule of Available-for-sale Securities [Line Items]
Carrying Value	611,720	526,238
Residential
Schedule of Available-for-sale Securities [Line Items]
Principal balance	1,445,079	1,808,992
Credit reserve	(70,067)	(116,870)
Unamortized discount, net	(296,342)	(298,469)
Amortized cost	1,078,670	1,393,653
Amortized cost	1,078,670	1,393,653
Gross unrealized gains	191,750	187,786
Gross unrealized losses	(2,796)	(23,133)
Carrying Value	1,267,624	1,558,306
Residential \| Senior Securities \| Prime
Schedule of Available-for-sale Securities [Line Items]
Principal balance	311,573	670,051
Credit reserve	(3,660)	(10,144)
Unamortized discount, net	(34,782)	(44,133)
Amortized cost	273,131	615,774
Amortized cost	273,131	615,774
Gross unrealized gains	35,980	47,980
Gross unrealized losses	(1,298)	(1,448)
Carrying Value	307,813	662,306
Residential \| Senior Securities \| Non-prime
Schedule of Available-for-sale Securities [Line Items]
Principal balance	196,258	218,603
Credit reserve	(9,644)	(13,840)
Unamortized discount, net	(31,491)	(36,882)
Amortized cost	155,123	167,881
Amortized cost	155,123	167,881
Gross unrealized gains	24,682	25,654
Gross unrealized losses	(61)	(149)
Carrying Value	179,744	193,386
Residential \| Re-REMIC
Schedule of Available-for-sale Securities [Line Items]
Principal balance	195,098	214,046
Credit reserve	(15,202)	(30,429)
Unamortized discount, net	(79,611)	(80,188)
Amortized cost	100,285	103,429
Amortized cost	100,285	103,429
Gross unrealized gains	68,062	72,947
Carrying Value	168,347	176,376
Residential \| Subordinate Securities
Schedule of Available-for-sale Securities [Line Items]
Principal balance	742,150	706,292
Credit reserve	(41,561)	(62,457)
Unamortized discount, net	(150,458)	(137,266)
Amortized cost	550,131	506,569
Amortized cost	550,131	506,569
Gross unrealized gains	63,026	41,205
Gross unrealized losses	(1,437)	(21,536)
Carrying Value	$ 611,720	$ 526,238

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

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Available For Sale Securities Principal Balance

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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

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-Section 50

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

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

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