Supplemental Guarantor Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Crrent assets	$ 561,288	$ 988,369
Total assets	1,501,079	1,993,230	$ 2,215,962
Current liabilities	194,049	324,487
Total liabilities not subject to compromise	503,932	1,943,657
Obligor Group [Member]
Condensed Financial Statements, Captions [Line Items]
Crrent assets	377,166	789,562
Noncurrent assets	1,079,397	1,134,238
Total assets	1,456,563	1,923,800
Current liabilities	141,676	261,743
Noncurrent liabilities	4,282,311	2,039,138
Total liabilities not subject to compromise	$ 4,423,987	$ 2,300,881