| **Employee Benefit Plan - Plan Assets at Fair Value (Details) (USD $)** | Dec. 31, 2014                                                                                                                         | Dec. 31, 2013                                                                                                                                                                                                                           | Dec. 31, 2012                                                                                                                               |
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| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               | $ 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets                                                                                    | $ 58,648,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets                                                                                                                                                                             | $ 60,097,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets                                                                                 |
| Level 1                                                                 |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 58,648,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member                                                                                          |                                                                                                                                        |
| Level 3                                                                 |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member                                                                                                   | 927,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member |
| Cash                                                                    |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 115,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_CashMember                                                                                                         |                                                                                                                                        |
| Cash | Level 1                                                          |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 115,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_CashMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member                    |                                                                                                                                        |
| Cash | Level 2                                                          |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_CashMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member                          |                                                                                                                                        |
| Cash | Level 3                                                          |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_CashMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member                          |                                                                                                                                        |
| Money market funds                                                      |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 697,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_MoneyMarketFundsMember                                                                                             |                                                                                                                                        |
| Money market funds | Level 1                                            |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 697,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_MoneyMarketFundsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member        |                                                                                                                                        |
| Money market funds | Level 2                                            |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_MoneyMarketFundsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member              |                                                                                                                                        |
| Money market funds | Level 3                                            |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_MoneyMarketFundsMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member              |                                                                                                                                        |
| U.S. treasury securities                                                |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 57,836,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_USTreasurySecuritiesMember                                                                                      |                                                                                                                                        |
| U.S. treasury securities | Level 1                                      |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 57,836,000us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_USTreasurySecuritiesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member |                                                                                                                                        |
| U.S. treasury securities | Level 2                                      |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_USTreasurySecuritiesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member          |                                                                                                                                        |
| U.S. treasury securities | Level 3                                      |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| **Defined Benefit Plan Disclosure [Line Items]**                        |                                                                                                                                  |                                                                                                                                                                                                                                    |                                                                                                                                        |
| Fair value of plan assets                                               |                                                                                                                                  | $ 0us-gaap_DefinedBenefitPlanFairValueOfPlanAssets/ us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis= us-gaap_USTreasurySecuritiesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member        |                                                                                                                                        |

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| - Definition
Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 50 -URI http://asc.fasb.org/extlink&oid=29635418&loc=d3e12355-114930
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