Supplemental Guarantor Information (Summarized Balance Sheets Information) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Current assets	$ 596,418	$ 988,369
Total assets	1,574,246	1,993,230
Current liabilities	228,932	324,487
Obligor Group [Member]
Condensed Financial Statements, Captions [Line Items]
Current assets	422,138	789,562
Noncurrent assets	1,086,516	1,134,238
Total assets	1,508,654	1,923,800
Current liabilities	176,423	261,743
Noncurrent liabilities	2,027,477	2,039,138
Total liabilities	$ 2,203,900	$ 2,300,881