Financial Instruments and Fair Value Measurements - Carrying Amount and Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Measurements [Line Items]
Pledged treasury securities, Carrying value	$ 26,404	$ 26,818
Retained interest investment, Carrying value	9,600	9,500
Level 1
Fair Value Measurements [Line Items]
Pledged treasury securities, Carrying value	26,404	26,818
Pledged treasury securities, Fair value	28,965	30,432
Level 3
Fair Value Measurements [Line Items]
Retained interest investment, Carrying value	9,567	9,481
Retained interest investment, Fair value	$ 12,711	$ 12,392

The carrying amount of securities categorized as held-to-maturity which serve as security for borrowings or other arrangements.

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

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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.

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 8: http://www.xbrl.org/2003/role/presentationRef

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+ Details

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the interests continued to be held by a transferor (retained or residual interest) after transferring financial assets to a third party.

+ References+ Details

- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References+ Details