Consolidated Statements of Income - USD ($) shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 297,687,000	$ 299,248,000	$ 313,139,000
Costs and expenses:
Instructional costs and services	115,280,000	116,161,000	117,013,000
Selling and promotional	57,042,000	58,335,000	59,095,000
General and administrative	74,456,000	69,024,000	68,666,000
Loss on disposals of long-lived assets	882,000	2,093,000	5,970,000
Impairment of goodwill	0	0	4,735,000
Depreciation and amortization	17,501,000	18,776,000	19,384,000
Total costs and expenses	265,161,000	264,389,000	274,863,000
Income from operations before interest income and income taxes	32,526,000	34,859,000	38,276,000
Interest income, net	2,915,000	185,000	116,000
Income from operations before income taxes	35,441,000	35,044,000	38,392,000
Income tax expense	9,287,000	11,493,000	14,940,000
Equity investment income (loss)	(515,000)	(2,430,000)	703,000
Net income	$ 25,639,000	$ 21,121,000	$ 24,155,000
Net income per common share:
Basic (in dollars per share)	$ 1.56	$ 1.30	$ 1.50
Diluted (in dollars per share)	$ 1.54	$ 1.29	$ 1.49
Weighted average number of shares outstanding:
Basic (in shares)	16,404	16,236	16,068
Diluted (in shares)	16,634	16,380	16,214