Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.7.0.1
Fair Value Measurements (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Fair value    
Investments available-for-sale $ 1,776 $ 1,776
U.S. government security funds    
Fair value    
Investments available-for-sale 1,776 1,776
Recurring basis | Level 1 - Quoted Prices in Active Markets for Identical Assets    
Fair value    
Trading investment securities 1,674 1,391
Total assets measured at fair value on a recurring basis 3,450 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 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 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 0
Total | Recurring basis    
Fair value    
Trading investment securities 1,674 1,391
Total assets measured at fair value on a recurring basis 3,450 3,167
Total | Recurring basis | U.S. government security funds    
Fair value    
Investments available-for-sale $ 1,776 $ 1,776