Fair Value of Financial Assets and Liabilities (Schedule of Financial Assets Measured at Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 40,000	$ 30,731
Other assets – advance payment to supplier	2,649	1,472
Total	42,649	32,203
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	40,000	30,731
Total	40,000	30,731
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other assets – advance payment to supplier	2,649	1,472
Total	$ 2,649	$ 1,472