Revenue from Contracts with Customers (Narrative 2) (Details) - Long-term Contract with Customer [Member] - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-10-01 $ in Millions	Sep. 30, 2021 USD ($)
Kaplan International [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 4.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Supplemental Education [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 9.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months