Income Taxes - Operating loss carry forwards (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Net operating loss carry forwards
Net operating loss carry forward	$ 6.4	$ 6.1
Valuation allowance	28.6	29.9
Foreign
Net operating loss carry forwards
Net operating loss carryforward, not subject to expiration	24.3
Net operating loss carryforward, subject to expiration	1.2
Operating loss carryforward	25.5
Tax credit carryforward	32.7	$ 33.5
Austrian Operations
Net operating loss carry forwards
Operating loss carryforward	24.3
Korean Operations
Net operating loss carry forwards
Operating loss carryforward	$ 1.2