Fair Value of Financial Assets and Liabilities (Schedule of Financial Assets Measured at Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		$ 40,000
Other asset – advance payment to supplier	$ 2,833	2,649
Total		42,649
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments		40,000
Total		40,000
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other asset – advance payment to supplier	$ 2,833	2,649
Total		$ 2,649