Income Taxes - Carryforwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Operating loss carryforwards
Operating loss carryforwards	$ 112,486
Maximum
Operating loss carryforwards
Net operating loss carryforwards, expiration period	20 years
Minimum
Operating loss carryforwards
Net operating loss carryforwards, expiration period	13 years
Non-U.S. jurisdictions
Operating loss carryforwards
Operating loss carryforwards	$ 76,375
U.S.
Operating loss carryforwards
Operating loss carryforwards	$ 36,111