Taxes (Schedule of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Tax loss carryforwards	$ 307,615	$ 271,405
Tax credit carryforwards	5,394	29,736
Investment in partnerships	193,217	308,653
Other	28,747	28,321
Gross deferred tax assets	534,973	638,115
Valuation allowance	(530,612)	(610,571)
Total deferred tax assets	4,361	27,544
Deferred tax liabilities:
Plant and equipment	3,037	3,674
Other	1,154	1,351
Total deferred tax liabilities	4,191	5,025
Net deferred tax asset	$ 170	$ 22,519