| **Financial Instruments and Fair Value Measurements - Carrying Amount and Fair Value of Financial Instruments (Details) (USD $)In Thousands, unless otherwise specified** | Mar. 31, 2014 | Dec. 31, 2013 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Carrying Value | Level 1                                                                                                                                                  |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                         |          |          |
| Pledged treasury securities                                                                                                                                               | $ 26,111      | $ 26,260      |
| Carrying Value | Level 3                                                                                                                                                  |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                         |          |          |
| Retained interest investment                                                                                                                                              | 9,684         | 9,639         |
| Fair Value | Level 1                                                                                                                                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                         |          |          |
| Pledged treasury securities                                                                                                                                               | 28,008        | 28,465        |
| Fair Value | Level 3                                                                                                                                                      |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                         |          |          |
| Retained interest investment                                                                                                                                              | $ 12,875      | $ 12,827      |

| X                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of interest continued to be held by a transferor after transferring financial assets to a third party.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 10 -Section 15 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=7502516&loc=d3e94415-111705
+ Details**Name:**us-gaap_RetainedInterestFairValueDisclosure**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
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)(i) -URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728
+ Details**Name:**us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |