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]: 2023-10-01 $ in Millions	Sep. 30, 2023 USD ($)
Kaplan International [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 300.9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	6 years
Supplemental Education [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 7.4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months