Quarterly Results of Operations (Unaudited) - Summarizes the Unaudited Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Statement [Abstract]
Net revenue	$ 162,443	$ 152,399	$ 141,463	$ 142,030	$ 141,298	$ 133,568	$ 119,260	$ 117,131
Costs and expenses:
Instructional costs and services	67,971	64,704	61,747	59,997	58,819	57,354	53,406	50,824	254,419	220,403	194,801
Admissions advisory and related	26,160	24,578	23,346	22,993	23,215	22,342	20,369	19,991	97,077	85,917	70,758
Advertising	15,038	15,498	14,520	15,929	13,008	12,909	11,467	13,639	60,985	51,023	45,587
Marketing and promotional	1,527	1,299	1,383	1,435	1,313	1,199	919	929
General and administrative	10,870	9,035	8,978	8,051	11,696	8,561	7,701	7,544	36,934	35,502	29,043
Total costs and expenses	121,566	115,114	109,974	108,405	108,051	102,365	93,862	92,927	455,059	397,205	344,581
Operating income	40,877	37,285	31,489	33,625	33,247	31,203	25,398	24,204	143,276	114,052	82,160
Interest expense	(609)	(528)	(439)	(668)	(260)	(154)	(78)	(207)
Interest and other income	104	1,502	62	2,195	19	16	26	10
Income before income taxes	40,372	38,259	31,112	35,152	33,006	31,065	25,346	24,007	144,895	113,424	81,528
Income tax expense	14,215	15,714	12,048	14,207	12,097	12,594	9,748	9,538	56,184	43,977	30,982
Net income	$ 26,157	$ 22,545	$ 19,064	$ 20,945	$ 20,909	$ 18,471	$ 15,598	$ 14,469	$ 88,711	$ 69,447	$ 50,546
Earnings per share:
Basic income per share	$ 0.58	$ 0.50	$ 0.43	$ 0.47	$ 0.47	$ 0.42	$ 0.35	$ 0.33	$ 1.98	$ 1.57	$ 1.13
Diluted income per share	$ 0.56	$ 0.49	$ 0.42	$ 0.46	$ 0.46	$ 0.41	$ 0.35	$ 0.32	$ 1.92	$ 1.53	$ 1.12
Basic weighted average shares outstanding	45,026	44,963	44,681	44,242	44,167	44,365	44,447	44,371	44,731	44,332	44,631
Diluted weighted average shares outstanding	46,712	46,424	45,929	45,449	45,364	45,339	45,169	45,151	46,131	45,251	45,105