XML 71 R59.htm IDEA: XBRL DOCUMENT v3.10.0.1
Fair Value Measurements (Fair Value of Available-for-sale Securities) (Details) - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Cost $ 830 $ 830
Gross unrealized gains 0 102
Gross unrealized losses 86 0
Available-for-sale Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated fair value 744 932
Available-for-sale Securities [Member] | Level 1 [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Estimated fair value $ 744 $ 932