Significant Accounting Policies - Graduation Fund (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) item	Mar. 31, 2016 USD ($)	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	5,702,000	4,755,000
Benefit redeemed	(3,563,000)	(2,427,000)
Balance at end of year	31,638,000	$ 23,265,000
Current Liability [Member]
Graduation fund estimated to be redeemed	16,600,000
Other Assets [Member]
Restricted cash
Funds payable for students who withdraw from the University	0
Minimum protective endowment	$ 500,000
Other Current Assets [Member]
Restricted cash
Funds payable for students who withdraw from the University			$ 13,000