Fair Value Measurements (Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Liabilities:
Contingent earn-out	$ 1,885	$ 2,372
Recurring
Assets:
Total assets	2,853	2,828
Liabilities:
Total liabilities	1,885	2,372
Recurring | Money market funds
Assets:
Money market funds	2,853	2,828
Recurring | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Contingent earn-out
Liabilities:
Contingent earn-out	1,885	2,372
Recurring | Convertible senior note
Liabilities:
Convertible senior note net	171,294	0
Recurring | Level 1
Assets:
Total assets	2,853	2,828
Liabilities:
Total liabilities	0	0
Recurring | Level 1 | Money market funds
Assets:
Money market funds	2,853	2,828
Recurring | Level 1 | Foreign currency derivative contracts
Assets:
Foreign currency derivative contracts	0	0
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Level 1 | Contingent earn-out
Liabilities:
Contingent earn-out	0	0
Recurring | Level 1 | Convertible senior note
Liabilities:
Convertible senior note net	0	0
Recurring | Level 2
Assets:
Total assets	0	0
Liabilities:
Total liabilities	0	0
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
Liabilities:
Foreign currency derivative contracts	0	0
Recurring | Level 2 | Contingent earn-out
Liabilities:
Contingent earn-out	0	0
Recurring | Level 2 | Convertible senior note
Liabilities:
Convertible senior note net	171,294	0
Recurring | Level 3
Assets:
Total assets	0	0
Liabilities:
Total liabilities	1,885	2,372
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
Recurring | Level 3 | Contingent earn-out
Liabilities:
Contingent earn-out	1,885	2,372
Recurring | Level 3 | Convertible senior note
Liabilities:
Convertible senior note net	$ 0	$ 0