Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements and Derivative Instruments (Carrying Amounts and Fair Value of the Financial Instruments) (Details)

v3.6.0.2
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%