Debt Obligations - Repurchase Obligations Outstanding (Detail) (Repurchase Agreements [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Revolving Repurchase Facilities [Member]
Credit Facilities [Line Items]
Maximum Facility Size	$ 1,362,000
Principal Balance	890,636
Net Book Value	886,447
Potential	683,858
Current	339,317
Available	344,541
Asset-Specific Repurchase Agreements [Member]
Credit Facilities [Line Items]
Maximum Facility Size	1,696,721
Principal Balance	1,291,988
Net Book Value	1,285,891
Potential	1,018,579
Current	643,040
Available	344,541
Bank of America [Member] \| Revolving Repurchase Facilities [Member]
Credit Facilities [Line Items]
Maximum Facility Size	500,000
Principal Balance	278,811
Net Book Value	277,336
Potential	210,930
Current	59,404
Available	151,526
Citibank [Member] \| Revolving Repurchase Facilities [Member]
Credit Facilities [Line Items]
Maximum Facility Size	500,000
Principal Balance	232,875
Net Book Value	232,162
Potential	176,168
Current	5,000
Available	171,168
JP Morgan [Member] \| Revolving Repurchase Facilities [Member]
Credit Facilities [Line Items]
Maximum Facility Size	362,000
Principal Balance	378,950
Net Book Value	376,949
Potential	296,760
Current	274,913
Available	21,847
Wells Fargo [Member] \| Asset-Specific Repurchase Agreements [Member]
Credit Facilities [Line Items]
Maximum Facility Size	334,721
Principal Balance	401,352
Net Book Value	399,444
Potential	334,721
Current	303,723
Available

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Repurchase Facility Maximum Borrowing Capacity

+ References

No definition available.

+ Details

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Balance Type:	credit
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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

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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

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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=28368275&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=7523297&loc=SL6224234-111729

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- Definition

The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 10

-Section 05

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=7517284&loc=d3e93645-111703

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