| **Condensed Financial Information (parent company only) - Balance Sheet (Details) (USD $)In Thousands, unless otherwise specified** | Dec. 31, 2014                                                                                                                  | Dec. 31, 2013                                                                                                                  | Dec. 31, 2012                     | Dec. 31, 2011                     |
|-------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|-----------------------------------|-----------------------------------|
| **ASSETS**                                                                                                                          |                                                                                                                           |                                                                                                                           |                              |                              |
| Goodwill                                                                                                                            | $ 202,724us-gaap_Goodwill                                                                                                      | $ 188,948us-gaap_Goodwill                                                                                                      | $ 141,375us-gaap_Goodwill         |                              |
| Other assets                                                                                                                        | 20,764us-gaap_OtherAssets                                                                                                      | 28,997us-gaap_OtherAssets                                                                                                      |                              |                              |
| TOTAL ASSETS                                                                                                                        | 5,824,127us-gaap_Assets                                                                                                        | 5,437,262us-gaap_Assets                                                                                                        |                              |                              |
| **LIABILITIES**                                                                                                                     |                                                                                                                           |                                                                                                                           |                              |                              |
| Borrowings                                                                                                                          | 411,994us-gaap_DebtAndCapitalLeaseObligations                                                                                  | 523,264us-gaap_DebtAndCapitalLeaseObligations                                                                                  |                              |                              |
| Other liabilities                                                                                                                   | 41,411us-gaap_OtherLiabilities                                                                                                 | 45,836us-gaap_OtherLiabilities                                                                                                 |                              |                              |
| Total liabilities                                                                                                                   | 5,097,300us-gaap_Liabilities                                                                                                   | 4,802,339us-gaap_Liabilities                                                                                                   |                              |                              |
| Stockholders' equity                                                                                                                | 726,827us-gaap_StockholdersEquity                                                                                              | 634,923us-gaap_StockholdersEquity                                                                                              | 552,236us-gaap_StockholdersEquity | 514,467us-gaap_StockholdersEquity |
| Total liabilities and stockholders' equity                                                                                          | 5,824,127us-gaap_LiabilitiesAndStockholdersEquity                                                                              | 5,437,262us-gaap_LiabilitiesAndStockholdersEquity                                                                              |                              |                              |
| Parent                                                                                                                              |                                                                                                                           |                                                                                                                           |                              |                              |
| **ASSETS**                                                                                                                          |                                                                                                                           |                                                                                                                           |                              |                              |
| Cash                                                                                                                                | 36,044us-gaap_Cash/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                           | 13,228us-gaap_Cash/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                           |                              |                              |
| Investment in subsidiaries                                                                                                          | 820,123us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember | 745,818us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember |                              |                              |
| Goodwill                                                                                                                            | 448us-gaap_Goodwill/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                          | 448us-gaap_Goodwill/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                          |                              |                              |
| Other assets                                                                                                                        | 6,281us-gaap_OtherAssets/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                     | 8,695us-gaap_OtherAssets/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                     |                              |                              |
| TOTAL ASSETS                                                                                                                        | 862,896us-gaap_Assets/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                        | 768,189us-gaap_Assets/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                        |                              |                              |
| **LIABILITIES**                                                                                                                     |                                                                                                                           |                                                                                                                           |                              |                              |
| Borrowings                                                                                                                          | 126,702us-gaap_DebtAndCapitalLeaseObligations/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                | 126,702us-gaap_DebtAndCapitalLeaseObligations/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                |                              |                              |
| Other liabilities                                                                                                                   | 9,367us-gaap_OtherLiabilities/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                | 6,564us-gaap_OtherLiabilities/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                |                              |                              |
| Total liabilities                                                                                                                   | 136,069us-gaap_Liabilities/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                   | 133,266us-gaap_Liabilities/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                                   |                              |                              |
| Stockholders' equity                                                                                                                | 726,827us-gaap_StockholdersEquity/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                            | 634,923us-gaap_StockholdersEquity/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                                            |                              |                              |
| Total liabilities and stockholders' equity                                                                                          | $ 862,896us-gaap_LiabilitiesAndStockholdersEquity/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                            | $ 768,189us-gaap_LiabilitiesAndStockholdersEquity/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember                            |                              |                              |

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| - Definition
Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
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| - Definition
Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.
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| - Definition
Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.
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| - Definition
Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
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| - Definition
Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.
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| - Definition
Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.
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Amount of liabilities and equity items, including the portion of equity attributable to noncontrolling interests, if any.
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The aggregate carrying amounts, as of the balance sheet date, of assets not separately disclosed in the balance sheet.
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The aggregate carrying amount, as of the balance sheet date, of liabilities not separately disclosed in the balance sheet.
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| - Definition
Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.
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