| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K/A | 10-K |
| REVENUE | 348.3 | 335.3 | 293.1 | 273.3 | | 261.9 | 285.6 | 306.1 |
| REVENUE growth | 3.9% | 14.4% | 7.2% | | -100.0% | -8.3% | -6.7% | 40.4% |
| COSTS AND EXPENSES: | | | | | | | | |
| Educational services and facilities | 148.7 | 138.9 | 122.2 | 123.5 | | 129.4 | | 151.6 |
| Selling, general and administrative | 182.4 | 168.9 | 156.2 | 145.2 | | 138.8 | 148.4 | 151.8 |
| Gain on sale of assets | -0.2 | -22.5 | -0.1 | -0.6 | | -1.6 | 0.2 | 1.7 |
| Total costs & expenses | 332.0 | 286.1 | 278.3 | 268.1 | | 266.6 | 314.5 | 305.4 |
| OPERATING INCOME | 16.3 | 49.3 | 14.8 | 5.2 | | -4.7 | -28.9 | 0.7 |
| Operating margin | 4.7% | 14.7% | 5.0% | 1.9% | | -1.8% | -10.1% | 0.2% |
| |
| OTHER: | | | | | | | | |
| Interest income | 0.3 | | | 0.0 | | 0.1 | 0.2 | 0.1 |
| Interest expense | -0.2 | -2.0 | -1.3 | -3.0 | | -7.1 | | -8.0 |
| INCOME (LOSS) BEFORE INCOME TAXES | 16.4 | 47.2 | 13.5 | 2.3 | | -11.8 | | -3.1 |
| PROVISION (BENEFIT) FOR INCOME TAXES | 3.8 | 12.5 | -35.1 | 0.3 | | -0.3 | 0.2 | 0.2 |
| NET INCOME | 12.6 | 34.7 | 48.6 | 2.0 | -11.5 | -11.5 | -28.3 | -3.4 |
| PREFERRED STOCK DIVIDENDS | 1.1 | 1.2 | 1.4 | | | | | |
| INCOME (LOSS) AVAILABLE TO COMMON SHAREHOLDERS | 11.5 | 33.5 | 47.2 | 2.0 | | | | |
| |
| Basic | | | | | | | | |
| Net income (loss) per common share (in dollars per share) | $0.36 | $1.04 | $1.49 | $0.08 | ($0.48) | ($0.48) | ($1.21) | ($0.14) |
| |
| Diluted | | | | | | | | |
| Net income (loss) per common share (in dollars per share) | $0.36 | $1.04 | $1.49 | $0.08 | ($0.48) | ($0.48) | ($1.21) | ($0.14) |
| |
| Weighted average number of common shares outstanding: | | | | | | | | |
| Basic (in shares) | 25.9 | 25.1 | 24.7 | 24.6 | 23.9 | 23.9 | 23.5 | 23.2 |
| Diluted (in shares) | 25.9 | 25.1 | 24.7 | 24.6 | 23.9 | 23.9 | 23.5 | 23.2 |