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Debt (Schedule of Obligations Under Debt Arrangements) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 17, 2020	Jan. 16, 2020
Debt Instrument [Line Items]
Principal	$ 3,389,743	$ 3,431,302
Unamortized Premium and Debt Issuance Costs	30,166	37,586
Net Value	3,359,577	3,393,716
Credit Facility \| Term Loan
Debt Instrument [Line Items]
Principal	300,000	0
Unamortized Premium and Debt Issuance Costs	2,423	0
Net Value	297,577	0
Credit Facility \| Revolving Credit Facility \| Revolving Loan
Debt Instrument [Line Items]
Principal	133,000	643,700
Unamortized Premium and Debt Issuance Costs	0	0
Net Value	133,000	643,700
Unamortized debt issuance costs	5,200	$ 5,800
Credit Facility \| Revolving Credit Facility \| Term Loan
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ 2,400
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	2,320	2,963
Net Value	$ 338,815	$ 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	4,749	5,639
Net Value	$ 530,085	$ 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	3,605	4,189
Net Value	$ 356,194	$ 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	6,993	13,022
Net Value	$ 993,007	$ 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	10,076	11,269
Net Value	$ 710,899	$ 709,706