Unaudited Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 188,279	$ 162,283
Tuition receivable, net	14,962us-gaap_AccountsReceivableNetCurrent	16,942us-gaap_AccountsReceivableNetCurrent
Other current assets	14,342us-gaap_OtherAssetsCurrent	17,426us-gaap_OtherAssetsCurrent
Total current assets	217,583us-gaap_AssetsCurrent	196,651us-gaap_AssetsCurrent
Property and equipment, net	80,804us-gaap_PropertyPlantAndEquipmentNet	82,266us-gaap_PropertyPlantAndEquipmentNet
Deferred income taxes	17,013us-gaap_DeferredTaxAssetsNetNoncurrent	16,241us-gaap_DeferredTaxAssetsNetNoncurrent
Goodwill	6,800us-gaap_Goodwill	6,800us-gaap_Goodwill
Other assets	5,578us-gaap_OtherAssetsNoncurrent	5,857us-gaap_OtherAssetsNoncurrent
Total assets	327,778us-gaap_Assets	307,815us-gaap_Assets
Current liabilities:
Accounts payable and accrued expenses	42,905	43,836
Income taxes payable	8,539us-gaap_TaxesPayableCurrent	1,286us-gaap_TaxesPayableCurrent
Deferred revenue	5,583us-gaap_DeferredRevenueCurrent	4,682us-gaap_DeferredRevenueCurrent
Other current liabilities	281us-gaap_OtherLiabilitiesCurrent	281us-gaap_OtherLiabilitiesCurrent
Current portion of term loan	6,250us-gaap_LongTermDebtCurrent	6,250us-gaap_LongTermDebtCurrent
Total current liabilities	63,558us-gaap_LiabilitiesCurrent	56,335us-gaap_LiabilitiesCurrent
Term loan, less current portion	110,938us-gaap_LongTermDebtNoncurrent	112,500us-gaap_LongTermDebtNoncurrent
Other long-term liabilities	46,919	46,248
Total liabilities	221,415us-gaap_Liabilities	215,083us-gaap_Liabilities
Commitments and contingencies
Stockholders' equity:
Common stock, par value $0.01; 20,000,000 shares authorized; 10,903,341 and 10,974,034 shares issued and outstanding at December 31, 2014 and March 31, 2015, respectively	110us-gaap_CommonStockValue	109us-gaap_CommonStockValue
Additional paid-in capital	17,000	14,550
Retained earnings	89,370	77,985
Accumulated other comprehensive income (loss)	(117)	88
Total stockholders' equity	106,363us-gaap_StockholdersEquity	92,732us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 327,778	$ 307,815

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

Name:	us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant