Fair Value Measurements - Fair Value of Non-Current Financial Liabilities (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt $ 1,300,000 $ 1,300,000
Fair Value | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term debt $ 1,347,600 $ 1,302,000