Revenue from Contract with Customer (Narrative 2) (Details) - Long-term Contract with Customer [Member] - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 $ in Millions	Dec. 31, 2023 USD ($)
Kaplan International [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 311.6
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	$ 7.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months