Fair Value Measurements (Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Restricted cash balance	$ 216	$ 1,451
Recurring
Assets:
Assets	2,817	2,871
Liabilities:
Liabilities	0	2
Recurring | Money market funds
Assets:
Money market funds	2,817	2,806
Recurring | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	65
Liabilities:
Foreign currency derivative contracts	0	2
Recurring | Level 1
Assets:
Assets	2,817	2,806
Liabilities:
Liabilities	0	0
Recurring | Level 1 | Money market funds
Assets:
Money market funds	2,817	2,806
Recurring | Level 1 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Level 2
Assets:
Assets	0	65
Liabilities:
Liabilities	0	2
Recurring | Level 2 | Money market funds
Assets:
Money market funds	0	0
Recurring | Level 2 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	65
Liabilities:
Foreign currency derivative contracts	0	2
Recurring | Level 3
Assets:
Assets	0	0
Liabilities:
Liabilities	0	0
Recurring | Level 3 | Money market funds
Assets:
Money market funds	0	0
Recurring | Level 3 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	$ 0	$ 0