Significant Accounting Policies - Graduation Fund (Details)	6 Months Ended
	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)	Dec. 31, 2016 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	12 months
Balance at beginning of year	$ 29,499,000	$ 20,937,000
Revenue deferred	11,982,000	10,128,000
Benefit redeemed	(7,719,000)	(5,806,000)
Balance at end of year	33,762,000	$ 25,259,000
Current Liability [Member]
Graduation fund estimated to be redeemed	17,600,000
Other Assets [Member]
Restricted cash
Minimum protective endowment	500,000
Other Current Assets [Member]
Restricted cash
Funds payable for students who withdraw from the University	$ 15,000		$ 13,000