Fair Value Measurements (Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	$ 1,217,896	$ 1,517,631
Fair Value | Senior notes (Level 1) | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	570,339	576,875
Fair Value | Revolving credit facilities and term loans (Level 2) | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	647,557	940,756
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	1,154,346	1,450,234
Carrying Value | Senior notes (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	519,803	519,211
Carrying Value | Revolving credit facilities and term loans (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total financial instruments	$ 634,543	$ 931,023