Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements of Income [Abstract]
Revenues	$ 454,851	$ 441,088	$ 434,437
Costs and expenses:
Instruction and educational support	245,177	241,026	234,097
Marketing	82,574	79,025	70,084
Admissions advisory	19,494	17,832	16,304
General and administration	55,397	45,733	44,254
Total costs and expenses	402,642	383,616	364,739
Income from operations	52,209	57,472	69,698
Investment income	1,079	462	283
Interest expense	642	642	3,850
Income before income taxes	52,646	57,292	66,131
Provision for income taxes	32,034	22,490	26,108
Net income	$ 20,612	$ 34,802	$ 40,023
Earnings per share:
Basic	$ 1.93	$ 3.28	$ 3.78
Diluted	$ 1.84	$ 3.21	$ 3.73
Weighted average shares outstanding:
Basic	10,678	10,610	10,588
Diluted	11,199	10,845	10,740