Income Taxes - NOL Carryforwards (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Operating loss carryforwards
Net operating loss carryforwards	$ 434,900
Valuation allowance offsetting the deferred tax assets	123,652	$ 139,795
SPAIN
Operating loss carryforwards
Net operating loss carryforwards	89,600
Other non-U.S. Countries
Operating loss carryforwards
Net operating loss carryforwards	179,700
US
Operating loss carryforwards
Net operating loss carryforwards	73,300
Velardena properties | Mexico
Operating loss carryforwards
Net operating loss carryforwards	79,800
Other Mexico activities | Mexico
Operating loss carryforwards
Net operating loss carryforwards	$ 12,500