Commitments and Contingencies - Standby Letters of Credit, Surety Bonds and Other Commitments (Details) € in Thousands, $ in Thousands	1 Months Ended
	Oct. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Mar. 11, 2020 EUR (€)
Foreign Tax Authority | Tax Authority, Spain | Subsequent Event
Debt Instrument [Line Items]
Income Tax Examination, Tax Expense Paid, Pending Appeal	$ 9,300
Cash Collateralized Letter Of Credit - Spain Tax Audits
Debt Instrument [Line Items]
Letters of credit outstanding, amount		$ 11,000	$ 11,500
Cash Collateralized Letter Of Credit - Spain Tax Audits, Extension of Audit
Debt Instrument [Line Items]
Letters of credit outstanding, amount		25,300		€ 21,600
Kendall College, St. Augustine, Walden University, and NewSchool of Architecture and Design
Debt Instrument [Line Items]
Letters of credit outstanding, amount		$ 83,600	$ 83,600