Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value) (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 37,918	$ 43,191
Level 1
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	37,918	43,191
Level 2
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	0	0
Level 3
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 0	$ 0