Equity Investees (Schedule of Balance Sheet Information for Equity Investees) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets
Current assets	$ 644,143	$ 580,169
Fixed assets, net	3,825,124	3,851,334
Total assets	5,949,613	5,933,619
LIABILITIES AND CAPITAL
Current liabilities	454,094	383,411
Total liabilities and equity	5,949,613	5,933,619
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Poseidon
Assets
Current assets	17,531	30,465
Fixed assets, net	168,723	171,732
Other assets	5,036	4,673
Total assets	191,290	206,870
LIABILITIES AND CAPITAL
Current liabilities	11,720	9,958
Other liabilities	229,008	237,595
Equity	(49,438)	(40,683)
Total liabilities and equity	$ 191,290	$ 206,870