Other Long-Term Liabilities - Deferred (Details)		1 Months Ended		12 Months Ended
	Jan. 13, 2016 USD ($)	Aug. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Dec. 31, 2017 USD ($) item	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Minimum
Leasehold improvements and long-term liability amortization period				5 years
Maximum
Leasehold improvements and long-term liability amortization period				10 years
New York Code And Design Academy, Inc.
Deferred payment arrangements value				$ 0
Total potential cash payments for acquisition				25,000,000
Contingent consideration payment	$ 4,600,000	$ 500,000	$ 6,000,000	0
New York Code And Design Academy, Inc. | Maximum
Contingent consideration				11,500,000	$ 11,500,000
Jack Welch Management Institute
Funds received from investor				$ 2,800,000
Deferred payment arrangement number of sellers | item				1
Deferred payment arrangements value				$ 3,600,000		$ 3,400,000