Equity Investees (Schedule of Balance Sheet Information for Equity Investees) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Current assets	$ 496,880	$ 593,074
Fixed assets, net	4,256,491	4,294,475
Total assets	6,434,458	6,597,641
LIABILITIES AND CAPITAL
Current liabilities	324,809	415,495
Total liabilities and equity	6,434,458	6,597,641
Equity Method Investment, Nonconsolidated Investee or Group of Investees | Poseidon
Assets
Current assets	20,112	30,307
Fixed assets, net	183,268	187,091
Other assets	2,014	2,113
Total assets	205,394	219,511
LIABILITIES AND CAPITAL
Current liabilities	15,135	15,558
Other liabilities	236,659	245,976
Equity	(46,400)	(42,023)
Total liabilities and equity	$ 205,394	$ 219,511