v3.10.0.1

Segment and Geographic Information - Concentration Risk (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($) university_client	Sep. 30, 2018 USD ($) segment university_client	Sep. 30, 2017 USD ($) university_client	Dec. 31, 2017 USD ($) university_client
Segment Information
Number of operating segments (in segments) | segment			2
Number of reportable segments (in segments) | segment			2
Revenue	$ 106,963	$ 70,250	$ 296,674	$ 200,074
Accounts receivable, net	49,651		49,651		$ 14,174
Graduate Program Segment
Segment Information
Revenue	89,719	65,924	251,487	195,748
Accounts receivable, net	22,397		22,397		12,520
Short Course Segment
Segment Information
Revenue	17,244	$ 4,326	45,187	$ 4,326
Accounts receivable, net	1,435		$ 1,435		$ 988
Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Number of clients who account for more then 10% (in clients) | university_client		4	3	4
Credit concentration risk | Accounts receivable, net | Graduate Program Segment
Segment Information
Number of clients who account for more then 10% (in clients) | university_client			2		2
University client A | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue	$ 24,000	$ 19,600	$ 65,000	$ 58,400
Percentage of concentration of credit risk	22.00%	28.00%	22.00%	30.00%
University client A | Customer concentration risk | Revenue segment | Short Course Segment
Segment Information
Percentage of concentration of credit risk	91.00%	82.00%	82.00%
University client A | Credit concentration risk | Accounts receivable, net | Graduate Program Segment
Segment Information
Percentage of concentration of credit risk			27.00%		67.00%
Accounts receivable, net	$ 13,400		$ 13,400		$ 9,400
University client B | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue	$ 13,000	$ 10,800	$ 39,500	$ 34,600
Percentage of concentration of credit risk	12.00%	15.00%	13.00%	17.00%
University client B | Credit concentration risk | Accounts receivable, net | Graduate Program Segment
Segment Information
Percentage of concentration of credit risk			14.00%		14.00%
Accounts receivable, net	$ 7,000		$ 7,000		$ 2,000
University client C | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue	$ 10,800	$ 7,200	$ 30,600	$ 21,000
Percentage of concentration of credit risk	10.00%	10.00%	10.00%	11.00%
University client D | Customer concentration risk | Revenue | Graduate Program Segment
Segment Information
Revenue		$ 7,100		$ 20,300
Percentage of concentration of credit risk		10.00%		10.00%

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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.

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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.

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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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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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