Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.8.0.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Fair value    
Investments available-for-sale   $ 1,776
U.S. government security funds    
Fair value    
Investments available-for-sale   1,776
Recurring basis | Total    
Fair value    
Trading investment securities $ 1,907 1,391
Total assets measured at fair value on a recurring basis 1,907 3,167
Recurring basis | Total | U.S. government security funds    
Fair value    
Investments available-for-sale   1,776
Recurring basis | Level 1 - Quoted Prices in Active Markets for Identical Assets    
Fair value    
Trading investment securities 1,907 1,391
Total assets measured at fair value on a recurring basis 1,907 3,167
Recurring basis | Level 1 - Quoted Prices in Active Markets for Identical Assets | U.S. government security funds    
Fair value    
Investments available-for-sale   1,776
Recurring basis | Level 2 - Significant Other Observable Inputs    
Fair value    
Trading investment securities 0 0
Total assets measured at fair value on a recurring basis 0 0
Recurring basis | Level 2 - Significant Other Observable Inputs | U.S. government security funds    
Fair value    
Investments available-for-sale   0
Recurring basis | Level 3 - Significant Unobservable Inputs    
Fair value    
Trading investment securities 0 0
Total assets measured at fair value on a recurring basis $ 0 0
Recurring basis | Level 3 - Significant Unobservable Inputs | U.S. government security funds    
Fair value    
Investments available-for-sale   $ 0