Legal and Regulatory Matters - Turkish Regulation and Internal Investigation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Loss Contingencies [Line Items]
Assets	$ 7,782,564		$ 7,782,564		$ 7,062,470
Liabilities	5,883,427		5,883,427		6,041,245
Revenues	983,394	$ 929,855	3,116,766	$ 3,068,299
Operating (loss) income	(5,696)	$ 12,502	175,288	$ 211,913
Variable Interest Entity, Primary Beneficiary
Loss Contingencies [Line Items]
Assets	1,558,050		1,558,050		1,309,113
Liabilities	606,896		606,896		424,297
Variable Interest Entity, Primary Beneficiary | Istanbul Bilgi University
Loss Contingencies [Line Items]
Required reimbursement, other activities					8,000
Assets	134,000		134,000		83,000
Liabilities	117,000		117,000		63,000
Revenues					106,000
Operating (loss) income					26,000
Depreciation and amortization					6,000
Variable Interest Entity, Primary Beneficiary | Istanbul Bilgi University | Consolidation Eliminations
Loss Contingencies [Line Items]
Due to related party	$ 32,000		$ 32,000		19,000
Variable Interest Entity, Primary Beneficiary | Management, Operational And Student Services, And Intellectual Property | Subsidiary of Common Parent | Istanbul Bilgi University
Loss Contingencies [Line Items]
Required reimbursement from related party					$ 29,000