v3.8.0.1

Segment and Geographic Information - Concentration Risk (Details) $ in Thousands		3 Months Ended								12 Months Ended
	Jul. 01, 2017 segment	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) client	Dec. 31, 2016 USD ($) client	Dec. 31, 2015 USD ($)
Segment Information
Number of operating segments | segment	2
Number of reportable segments | segment	2
Revenue		$ 86,678	$ 70,250	$ 64,995	$ 64,829	$ 57,350	$ 51,960	$ 49,110	$ 47,444	$ 286,752	$ 205,864	$ 150,194
Accounts receivable, net		14,174				7,860				14,174	7,860
Graduate Program Segment
Segment Information
Revenue										270,432	$ 205,864	$ 150,194
Short Course Segment
Segment Information
Revenue										$ 16,320
Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Number of clients who account for more then 10% | client										4	3
Customer concentration risk | Revenue | Short Course Segment
Segment Information
Percentage of concentration of credit risk										82.00%
Credit concentration risk | Accounts receivable | Graduate Program Segment
Segment Information
Number of clients who account for more then 10% | client										2	2
University client A | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue										$ 77,600	$ 71,000
Percentage of concentration of credit risk										27.00%	35.00%
University client A | Credit concentration risk | Accounts receivable | Graduate Program Segment
Segment Information
Accounts receivable, net		9,400				5,800				$ 9,400	$ 5,800
Percentage of concentration of credit risk										67.00%	74.00%
University client B | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue										$ 48,200	$ 36,700
Percentage of concentration of credit risk										17.00%	18.00%
University client B | Credit concentration risk | Accounts receivable | Graduate Program Segment
Segment Information
Accounts receivable, net		$ 2,000				$ 1,400				$ 2,000	$ 1,400
Percentage of concentration of credit risk										14.00%	17.00%
University client C | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue										$ 30,100	$ 22,100
Percentage of concentration of credit risk										11.00%	11.00%
University client D | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue										$ 28,300
Percentage of concentration of credit risk										10.00%

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Number of clients for concentration risk

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Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-SubTopic 10
-Section 50
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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Aggregate revenue during the period from services rendered in the normal course of business, after deducting allowances and discounts.

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