XML 49 R37.htm IDEA: XBRL DOCUMENT v3.10.0.1
Revenue Recognition - Graduation Fund (Details)
$ in Thousands
 6 Months Ended
Jun. 30, 2018
USD ($)
item
Jun. 30, 2017
USD ($)
Consecutive terms of non attendance in which Graduation Fund credits will be lost | item 1  
Number of free courses | item 1  
Number of successfully completed courses | item 3  
Expected collection period of tuition receivable, current 12 months  
Graduation fund estimated to be redeemed $ 20,000  
Unbilled receivables 1,300  
Balance at beginning of year 37,400 $ 29,499
Revenue deferred 12,917 11,982
Benefit redeemed (10,497) (7,719)
Balance at end of year $ 39,820 $ 33,762
Minimum    
Expected redemption period of Graduation Fund, non-current 2 years  
Maximum    
Expected redemption period of Graduation Fund, non-current 4 years