| **Fair Value Measurements and Derivative Instruments (Carrying Amounts and Fair Value of the Financial Instruments) (Details) - USD ($) $ in Thousands** | Dec. 31, 2016 | Dec. 31, 2015 |
|----------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Carrying Amount                                                                                                                                          |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                        |          |          |
| Current and long-term debt                                                                                                                               | $ 1,336,772   | $ 1,332,738   |
| Fair Value                                                                                                                                               |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                        |          |          |
| Current and long-term debt                                                                                                                               | $ 1,393,865   | $ 1,390,743   |
| Senior Notes [Member] | 2021 Notes                                                                                                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                        |          |          |
| Stated percentage                                                                                                                                        | 6.75%         |          |
| Senior Notes [Member] | 2025 Notes                                                                                                                       |          |          |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                        |          |          |
| Stated percentage                                                                                                                                        | 6.875%        |          |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13476-108611
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
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