Legal and Regulatory Matters - United States Postsecondary Education Regulation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) program	Dec. 31, 2016	Dec. 31, 2017 USD ($)
Kendall College, St. Augustine, Walden University, and NewSchool of Architecture and Design
Loss Contingencies [Line Items]
Letters of credit outstanding, amount | $	$ 139,000		$ 136,900
United States
Loss Contingencies [Line Items]
Percentage of funds received		15.00%
Number of in the zone programs (program) | program	3