v3.19.3.a.u2

Segment and Geographic Information - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments (in segments) | segment									2
Revenue	$ 163,178	$ 153,798	$ 135,461	$ 122,234	$ 115,095	$ 106,963	$ 97,423	$ 92,288	$ 574,671	$ 411,769	$ 286,752
Accounts receivable, net	33,655				32,636				33,655	32,636
Graduate Program Segment
Segment Reporting Information [Line Items]
Revenue									417,206	348,361	270,432
Accounts receivable, net	3,454				31,110				3,454	31,110
Deferred revenue, recognized during period									2,400	2,500
Net capitalized contract acquisition costs	500				300				500	300
Additional net capitalized contract acquisition cost									200
Alternative Credential Segment
Segment Reporting Information [Line Items]
Revenue									157,465	63,408	16,320
Accounts receivable, net	12,436				982				12,436	982
Deferred revenue, recognized during period									5,400	4,500
Alternative Credential Segment | Non-US
Segment Reporting Information [Line Items]
Revenue									40,800	33,900	10,000
Long-lived assets	2,700				1,200				2,700	1,200
University client 1 | Revenue | Customer concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Revenue									$ 83,500	$ 86,900	$ 77,600
Percentage of concentration of credit risk									15.00%	21.00%	27.00%
University client 1 | Accounts receivable | Credit concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Percentage of concentration of credit risk									18.00%	36.00%
Accounts receivable, net	6,100				11,900				$ 6,100	$ 11,900
University client 2 | Revenue | Customer concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Revenue										$ 54,200	$ 48,200
Percentage of concentration of credit risk										13.00%	17.00%
University client 2 | Accounts receivable | Credit concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Percentage of concentration of credit risk									15.00%	36.00%
Accounts receivable, net	$ 4,900				$ 11,800				$ 4,900	$ 11,800
University client 3 | Revenue | Customer concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Revenue										$ 42,700	$ 30,100
Percentage of concentration of credit risk										10.00%	11.00%
University Client 4 | Revenue | Customer concentration risk | Graduate Program Segment
Segment Reporting Information [Line Items]
Revenue											$ 28,300
Percentage of concentration of credit risk											10.00%
1 University Client | Revenue | Customer concentration risk | Alternative Credential Segment
Segment Reporting Information [Line Items]
Percentage of concentration of credit risk									22.00%
1 University Client | Sales Revenue Segment Revenue | Customer concentration risk | Alternative Credential Segment
Segment Reporting Information [Line Items]
Revenue									$ 33,900
3 University Clients | Sales Revenue Segment Revenue | Customer concentration risk | Alternative Credential Segment
Segment Reporting Information [Line Items]
Percentage of concentration of credit risk									81.00%		82.00%

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