Consolidated Statements of Income - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 286,270,000	$ 297,687,000	$ 299,248,000
Costs and expenses:
Instructional costs and services	111,916,000	115,280,000	116,161,000
Selling and promotional	60,028,000	57,042,000	58,335,000
General and administrative	78,082,000	74,456,000	69,024,000
Loss on disposals of long-lived assets	556,000	882,000	2,093,000
Impairment of goodwill	7,336,000	0	0
Depreciation and amortization	15,596,000	17,501,000	18,776,000
Total costs and expenses	273,514,000	265,161,000	264,389,000
Income from operations before interest income and income taxes	12,756,000	32,526,000	34,859,000
Interest income, net	3,908,000	2,915,000	185,000
Income from operations before income taxes	16,664,000	35,441,000	35,044,000
Income tax expense	5,187,000	9,287,000	11,493,000
Equity investment loss	(1,464,000)	(515,000)	(2,430,000)
Net income	$ 10,013,000	$ 25,639,000	$ 21,121,000
Net income per common share:
Basic (in dollars per share)	$ 0.62	$ 1.56	$ 1.30
Diluted (in dollars per share)	$ 0.62	$ 1.54	$ 1.29
Weighted average number of shares outstanding:
Basic (in shares)	16,094,000	16,404,000	16,236,000
Diluted (in shares)	16,255,000	16,634,000	16,380,000