Equity Investees (Schedule of Operations for Equity Investees) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
INCOME STATEMENT DATA:
Revenues	$ 503,855	$ 388,467	$ 1,025,074	$ 928,390
Operating income	25,537	(278,220)	53,558	(219,058)
Net income	(41,682)	(326,714)	(75,906)	(301,805)
Poseidon
INCOME STATEMENT DATA:
Revenues	33,757	30,419	76,170	63,311
Operating income	24,636	21,922	56,797	45,528
Net income	$ 23,610	$ 20,636	$ 54,755	$ 42,219