Investments (Details) - Structured transactions - project finance loans (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2012 loans	Dec. 31, 2011 loans
Project Finance Loans:
Aggregate loan value	$ 36,960	$ 49,650
Aggregate loan net carrying amount	31,377	40,483
Allowance for loan losses rollforward:
Opening allowance for loan losses	9,167	9,167
Amounts charged off during the period	3,584	0
Closing allowance for loan losses	$ 5,583	$ 9,167
Other details:
Number of individual loan participations	4	6
Number of individual loan participations relating to the allowance for loan losses	1	2
Weighted average contractual term to maturity	0 years 10 months 24 days	2 years 1 month 6 days
Weighted average credit rating	BB	BB-
Range of individual credit ratings	BB+ to BB-	BB+ to CCC

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Reflects the amount of loans and leases that have been removed, or charged off, from both loan receivables and the reserve for credit losses, typically because they are considered to be not salvageable or have been purchased by unconsolidated collection entities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 210

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph 20

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-Article 9

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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- Definition

The allowance for loan and lease losses represents the reserve to cover probable credit losses related to specifically identified loans and leases, as well as probable credit losses inherent in the remainder of the loan portfolio as of the balance sheet date. For banks, include currently required allocated transfer risk reserves. Include carryover of or adjustments to the allowance for loan losses in connection with business combinations determined to be appropriate.

+ References

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Chapter V

-Section 563c.102

-Paragraph 8

-Subparagraph a(ii)

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-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

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-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section L

-Subsection 1

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

-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 Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 03

-Paragraph 7

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 8, 9

-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 Accounting Standards Codification

-Topic 310

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (b)(1)(ii)

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- Definition

Reflects the aggregate gross carrying amount of all categories of loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on loans and leases.

+ References

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

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 01-6

-Paragraph 13

-Subparagraph e

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

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Reflects the aggregate carrying amount of all categories of loans and leases held in portfolio, net of unearned income and the allowance for losses on loans and leases.

+ References

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- Definition

The number of individual project finance loans in which the Company participated.

+ References

No definition available.

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- Definition

The number of project finance loans to which the allowance for loan losses relates.

+ References

No definition available.

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- Definition

Range Of Individual Credit Ratings

+ References

No definition available.

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- Definition

Weighted Average Contractual Term To Maturity

+ References

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- Definition

Weighted average credit rating of deals within the structured project finance related transactions within Other Investments.

+ References

No definition available.

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