Quarterly Results of Operations (Unaudited) - Summarization of Unaudited Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Quarterly Results Of Operations [Line Items]
Net revenue	$ 141,298	$ 133,568	$ 119,260	$ 117,131	$ 113,005	$ 108,909	$ 103,118	$ 101,709	$ 511,257	$ 426,741	$ 385,625
Costs and expenses:
Instructional costs and services	58,819	57,354	53,406	50,824	50,639	48,933	46,354	48,875	220,403	194,801	178,844
Selling and promotional	37,536	36,450	32,755	34,559	31,166	31,248	27,709	29,832	141,300	119,955	112,493
General and administrative	11,696	8,561	7,701	7,544	8,028	7,145	7,038	6,832	35,502	29,043	26,621
Lease termination costs					(140)	922				782
Total costs and expenses	108,051	102,365	93,862	92,927	89,693	88,248	81,101	85,539	397,205	344,581	327,449
Operating income	33,247	31,203	25,398	24,204	23,312	20,661	22,017	16,170	114,052	82,160	58,176
Net interest expense	(241)	(138)	(52)	(197)	(404)	(150)	(3)	(75)
Income before income taxes	33,006	31,065	25,346	24,007	22,908	20,511	22,014	16,095	113,424	81,528	57,455
Income tax expense	12,097	12,594	9,748	9,538	7,584	7,643	9,141	6,614	43,977	30,982	22,249
Net income	$ 20,909	$ 18,471	$ 15,598	$ 14,469	$ 15,324	$ 12,868	$ 12,873	$ 9,481	$ 69,447	$ 50,546	$ 35,206
Earnings per share:
Basic income per share	$ 0.47	$ 0.42	$ 0.35	$ 0.33	$ 0.35	$ 0.29	$ 0.29	$ 0.21	$ 1.57	$ 1.13	$ 0.77
Diluted income per share	$ 0.46	$ 0.41	$ 0.35	$ 0.32	$ 0.34	$ 0.29	$ 0.29	$ 0.21	$ 1.53	$ 1.12	$ 0.76
Basic weighted average shares outstanding	44,167	44,365	44,447	44,371	44,317	44,302	44,658	45,590	44,332	44,631	45,722
Diluted weighted average shares outstanding	45,364	45,339	45,169	45,151	44,868	44,787	45,018	46,089	45,251	45,105	46,396

Costs directly attributable to educational services, including salaries and benefits for full-time faculty, administrators and academic advisors, and costs associated with adjunct faculty. Also includes costs for educational supplies such as books, costs associated with academic records and graduation, costs associated with collections from our students such as bad debt expense, and other university services such as evaluating transcripts.

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