Equity Investees (Schedule of Operations for Equity Investees) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
INCOME STATEMENT DATA:
Revenues	$ 518,821	$ 443,125	$ 1,543,895	$ 1,371,515
Operating income	34,494	4,032	88,052	(215,026)
Net income	(20,899)	(29,717)	(96,805)	(331,522)
Poseidon
INCOME STATEMENT DATA:
Revenues	27,262	35,351	103,432	98,662
Operating income	18,762	27,002	75,559	72,530
Net income	$ 17,718	$ 25,831	$ 72,473	$ 68,050