Significant Accounting Policies - Graduation Fund (Details)	9 Months Ended
	Sep. 30, 2017 USD ($) item	Sep. 30, 2016 USD ($)	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	17,494,000	14,753,000
Benefit redeemed	(12,551,000)	(9,139,000)
Balance at end of year	34,442,000	$ 26,551,000
Current Liability [Member]
Graduation fund estimated to be redeemed	19,300,000
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	$ 8,000		$ 13,000