Income Taxes - Carryforwards (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Maximum
Operating loss carryforwards
Net operating loss carryforwards, expiration period	20 years
Minimum
Operating loss carryforwards
Net operating loss carryforwards, expiration period	12 years
Research and development
Operating loss carryforwards
Tax credit carryforwards	$ 8,200
Non-U.S. jurisdictions
Operating loss carryforwards
Tax credit carryforwards	10,200
Operating loss carryforwards	68,878
U.S.
Operating loss carryforwards
Operating loss carryforwards	$ 41,037