Acquisition (Details) $ in Thousands		3 Months Ended								6 Months Ended	12 Months Ended
	Jan. 22, 2019 USD ($) Institution	Dec. 31, 2019 USD ($) item	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 ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Acquisition
Number of university partners | item		22									22
Goodwill		$ 160,766				$ 2,941					$ 160,766	$ 2,941
Assets acquired
Right-of-use assets		13,069									13,069
Liabilities assumed
Lease liability		13,069									13,069
Pro forma information
Net revenue		213,247	$ 193,289	$ 174,820	$ 197,287	177,548	$ 155,454	$ 236,818	$ 275,681	$ 512,499	778,643	845,501	$ 974,134
Pro forma, net revenue		213,247				195,656					781,893	907,960
Net income		76,669	58,151	51,112	73,243	75,531	33,761	46,038	73,681		259,175	229,011	203,319
Pro forma, net income		76,669				69,551					247,930	200,264
Amortization of intangible assets		2,179	2,179	2,179	1,686						8,223
Prior period adjustments
Technology and academic services		25,128	24,231	22,528	18,625	11,098	11,101	10,678	10,697		90,512	43,574	41,834
General and administrative		10,148	13,556	9,216	11,397	6,695	10,092	5,762	7,419		44,317	29,968	27,157
Marketing and communication		$ 33,863	$ 37,340	$ 35,726	$ 35,967	$ 27,252	$ 31,546	$ 30,095	$ 28,527		$ 142,896	117,420	$ 109,092
Orbis Education
Acquisition
Number of university partners	22	22									22
Purchase price	$ 361,184
Operating cash on hand used for acquisition	171,034
Goodwill	157,825
Transaction costs											$ 3,966	$ 808
Assets acquired
Cash	4,793
Cash, pledged collateral	300
Accounts receivable, net of allowance of $0	3,236
Accounts receivable, allowance	0
Property and equipment	5,392
Right-of-use assets	13,069
Intangible assets	210,280
Other assets	2,793
Liabilities assumed
Accounts payable	4,308
Accrued and other liabilities	4,451
Lease liability	13,069
Deferred tax liability	9,538	$ 9,538									9,538
Deferred revenue	45
Total net asset or liability purchased and assumed	208,152
Purchase price	365,977
Orbis Education | University partner relationships
Assets acquired
Intangible assets	210,000
Orbis Education | Credit facility
Acquisition
Purchase price	$ 191,000
Orbis Education
Pro forma information
Net revenue											85,869
Net income											(2,588)
Amortization of intangible assets											$ 8,223