Fair Value Measurements (Gross Amounts and Fair Value of Debt) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross value	$ 966,721	$ 967,661
6.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross value	452,836	452,836
Fair value - Level 2 | 6.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	459,629	464,157
Fair value - Level 2 | Term Loan Due 2026
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt instrument, fair value	461,078	460,023
Term Loan Due 2026 | Term loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gross value	$ 468,099	$ 469,411