Quarterly Results of Operations (Unaudited) - Summarizes the Unaudited Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net revenue	$ 213,247	$ 193,289	$ 174,820	$ 197,287	$ 177,548	$ 155,454	$ 236,818	$ 275,681	$ 512,499	$ 778,643	$ 845,501	$ 974,134
Costs and expenses:
Technology and academic services	25,128	24,231	22,528	18,625	11,098	11,101	10,678	10,697		90,512	43,574	41,834
Counseling services and support	59,957	56,249	54,299	53,093	51,989	51,116	50,838	50,747		223,598	204,690	188,595
Marketing and communication	33,863	37,340	35,726	35,967	27,252	31,546	30,095	28,527		142,896	117,420	109,092
General and administrative	10,148	13,556	9,216	11,397	6,695	10,092	5,762	7,419		44,317	29,968	27,157
Amortization of intangible assets	2,179	2,179	2,179	1,686						8,223
University related expenses					(405)	6,569	79,517	87,649			173,330	324,140
Loss on transaction			(122)	4,088	770	15,610	1,440	550		3,966	18,370	562
Total costs and expenses	131,275	133,555	123,826	124,856	97,399	126,034	178,330	185,589		513,512	587,352	691,380
Operating income	81,972	59,734	50,994	72,431	80,149	29,420	58,488	90,092		265,131	258,149	282,754
Interest income on Secured Note	14,872	16,208	14,482	13,735	13,699	13,248				59,297	26,947
Interest expense	(2,943)	(2,875)	(2,907)	(2,586)	(575)	(558)	(57)	(346)		(11,311)	(1,536)	(2,169)
Investment interest and other	343	255	2,668	1,119	521	371	1,567	981		4,385	3,440	2,943
Income before income taxes	94,244	73,322	65,237	84,699	93,794	42,481	59,998	90,727		317,502	287,000	283,528
Income tax expense	17,575	15,171	14,125	11,456	18,263	8,720	13,960	17,046		58,327	57,989	80,209
Net income	$ 76,669	$ 58,151	$ 51,112	$ 73,243	$ 75,531	$ 33,761	$ 46,038	$ 73,681		$ 259,175	$ 229,011	$ 203,319
Earnings per share:
Basic income per share	$ 1.61	$ 1.21	$ 1.07	$ 1.54	$ 1.58	$ 0.71	$ 0.97	$ 1.55		$ 5.42	$ 4.81	$ 4.31
Diluted income per share	$ 1.59	$ 1.20	$ 1.06	$ 1.52	$ 1.56	$ 0.70	$ 0.95	$ 1.52		$ 5.37	$ 4.73	$ 4.22
Basic weighted average shares outstanding	47,758	47,920	47,851	47,699	47,708	47,682	47,604	47,432		47,814	47,608	47,140
Diluted weighted average shares outstanding	48,112	48,337	48,313	48,274	48,422	48,422	48,411	48,397		48,266	48,414	48,235
Service [Member]
Net revenue	$ 213,247	$ 193,289	$ 174,820	$ 197,287	$ 177,548	$ 155,454				$ 778,643	$ 333,002
University Related Revenue [Member]
Net revenue							$ 236,818	$ 275,681			$ 512,499	$ 974,134