Taxes (Schedule of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Tax loss carryforwards	$ 352,342	$ 294,535
Tax credit carryforwards	3,117	5,297
Investment in partnerships	213,478	190,418
Other	19,377	20,387
Gross deferred tax assets	588,314	510,637
Valuation allowance	(573,995)	(506,316)	$ (530,600)
Total deferred tax assets	14,319	4,321
Deferred tax liabilities:
Plant and equipment	1,219	2,063
Convertible Notes	8,845
Other	4,218	2,178
Total deferred tax liabilities	14,282	4,241
Net deferred tax asset	$ 37	$ 80