Secured Financings - Revolving Repurchase Facilities Outstanding (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Maximum Facility Size	$ 3,377,205,000
Collateral Assets	3,121,541,000
Potential	2,425,350,000
Repurchase Borrowings Outstanding	2,040,783,000	863,622,000
Available	384,567,000
Wells Fargo [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	1,000,000,000
Collateral Assets	747,256,000
Potential	585,737,000
Repurchase Borrowings Outstanding	484,365,000
Available	101,372,000
Citibank [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	500,000,000
Collateral Assets	621,025,000
Potential	472,080,000
Repurchase Borrowings Outstanding	392,455,000	334,692,000
Available	79,625,000
Bank of America [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	500,000,000
Collateral Assets	557,810,000
Potential	441,201,000
Repurchase Borrowings Outstanding	389,347,000	271,320,000
Available	51,854,000
JP Morgan [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	488,155,000
Collateral Assets	544,654,000
Potential	422,249,000
Repurchase Borrowings Outstanding	341,487,000	257,610,000
Available	80,762,000
MetLife [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	500,000,000
Collateral Assets	476,499,000
Potential	366,902,000
Repurchase Borrowings Outstanding	305,889,000
Available	61,013,000
Morgan Stanley [Member]
Line of Credit Facility [Line Items]
Maximum Facility Size	389,050,000
Collateral Assets	174,297,000
Potential	137,181,000
Repurchase Borrowings Outstanding	127,240,000
Available	$ 9,941,000

Repurchase Facility Maximum Borrowing Capacity

No definition available.

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ 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 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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- Definition

Reflects the aggregate value of loans, trade receivables, securities and financial instruments that serve as collateral for obligations arising from a transfer of financial assets recorded as a secured borrowing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5086-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

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