XML 42 R31.htm IDEA: XBRL DOCUMENT v3.19.2
Fair Value Measurements (Fair Value of Marketable Securities) (Details) - USD ($)
$ in Thousands
Jun. 30, 2019
Dec. 31, 2018
Fair Value Measurements    
Estimated fair value of marketable securities $ 29,437 $ 25,493
Fair value, inputs, Level 1 [Member]    
Fair Value Measurements    
Estimated fair value of marketable securities 29,437 25,493
Fair value, inputs, Level 2 [Member]    
Fair Value Measurements    
Estimated fair value of marketable securities 0 0
Fair value, inputs, Level 3 [Member]    
Fair Value Measurements    
Estimated fair value of marketable securities $ 0 $ 0