Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value) (Details) - Recurring - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	$ 34,471	$ 37,918
Liabilities measured at fair value	0	0
Level 1
Financial Assets And Liabilities Measured At Fair Value
Marketable securities	34,471	37,918
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