Equity Investees (Schedule of Balance Sheet Information for Equity Investees) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets
Current assets	$ 481,683	$ 580,169
Fixed assets, net	3,890,684	3,851,334
Total assets	5,826,326	5,933,619
LIABILITIES AND CAPITAL
Current liabilities	378,119	383,411
Total liabilities and equity	5,826,326	5,933,619
Poseidon
Assets
Current assets	22,890	30,465
Fixed assets, net	164,096	171,732
Other assets	5,762	4,673
Total assets	192,748	206,870
LIABILITIES AND CAPITAL
Current liabilities	12,001	9,958
Other liabilities	237,507	237,595
Equity (Deficit)	(56,760)	(40,683)
Total liabilities and equity	$ 192,748	$ 206,870