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Debt (Schedule of Obligations Under Debt Arrangements) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Dec. 17, 2020	Jan. 16, 2020
Debt Instrument [Line Items]
Principal	$ 3,374,943	$ 3,431,302
Unamortized Premium and Debt Issuance Costs	31,801	37,586
Net Value	3,343,142	3,393,716
Credit Facility \| Term Loan
Debt Instrument [Line Items]
Principal	300,000	0
Unamortized Premium and Debt Issuance Costs	2,547	0
Net Value	297,453	0
Credit Facility \| Revolving Credit Facility \| Revolving Loan
Debt Instrument [Line Items]
Principal	118,200	643,700
Unamortized Premium and Debt Issuance Costs	0	0
Net Value	118,200	643,700
Unamortized debt issuance costs	5,500	$ 5,800
Credit Facility \| Revolving Credit Facility \| Term Loan
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 2,500
Senior Notes \| 6.000% senior unsecured notes due 2023
Debt Instrument [Line Items]
Interest rate	600.00%	600.00%	6.00%
Principal	$ 0	$ 80,859
Unamortized Premium and Debt Issuance Costs	0	504
Net Value	$ 0	$ 80,355
Senior Notes \| 5.625% senior unsecured notes due 2024
Debt Instrument [Line Items]
Interest rate	562.50%	562.50%
Principal	$ 341,135	$ 341,135
Unamortized Premium and Debt Issuance Costs	2,534	2,963
Net Value	$ 338,601	$ 338,172
Senior Notes \| 6.500% senior unsecured notes due 2025
Debt Instrument [Line Items]
Interest rate	650.00%	650.00%
Principal	$ 534,834	$ 534,834
Unamortized Premium and Debt Issuance Costs	5,046	5,639
Net Value	$ 529,788	$ 529,195
Senior Notes \| 6.250% senior unsecured notes due 2026
Debt Instrument [Line Items]
Interest rate	625.00%	625.00%
Principal	$ 359,799	$ 359,799
Unamortized Premium and Debt Issuance Costs	3,799	4,189
Net Value	$ 356,000	$ 355,610
Senior Notes \| 8.000% senior unsecured notes due 2027
Debt Instrument [Line Items]
Interest rate	800.00%	800.00%	8.00%
Principal	$ 1,000,000	$ 750,000
Unamortized Premium and Debt Issuance Costs	7,401	13,022
Net Value	$ 992,599	$ 736,978
Senior Notes \| 7.750% senior unsecured notes due 2028
Debt Instrument [Line Items]
Interest rate	775.00%	775.00%		7.75%
Principal	$ 720,975	$ 720,975
Unamortized Premium and Debt Issuance Costs	10,474	11,269
Net Value	$ 710,501	$ 709,706