Equity Investees (Schedule of Balance Sheet Information for Equity Investees) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets
Current assets	$ 619,721	$ 580,169
Fixed assets, net	3,874,647	3,851,334
Total assets	5,963,487	5,933,619
LIABILITIES AND CAPITAL
Current liabilities	520,003	383,411
Total liabilities and equity	5,963,487	5,933,619
Poseidon
Assets
Current assets	17,546	30,465
Fixed assets, net	167,764	171,732
Other assets	5,447	4,673
Total assets	190,757	206,870
LIABILITIES AND CAPITAL
Current liabilities	13,649	9,958
Other liabilities	229,836	237,595
Equity (Deficit)	(52,728)	(40,683)
Total liabilities and equity	$ 190,757	$ 206,870