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Cash and Cash Equivalents and Investments - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Y
Dec. 31, 2011
Dec. 31, 2010
Investment Securities [Line Items]      
Period cash equivalents and short-term investments have been in continuous unrealized loss position, years, maximum 1 year    
Cash and cash equivalents of not-for-profit schools with restrictions $ 87,200,000 $ 74,500,000  
Restricted cash 97,878,000 0  
Certificates of deposit 7,400,000    
Funds related to a legal matter 2,500,000    
Cumulative unrealized losses on municipal bonds (152,000) (40,000) 88,000
ARS investment loss 200,000    
Years ARS auction events have been failing 3    
Credit Agreement [Member]
     
Investment Securities [Line Items]      
Cash and cash equivalents of not-for-profit schools with restrictions 88,000,000    
US Treasury Bill [Member]
     
Investment Securities [Line Items]      
Period debt obligations mature, years, maximum 1 year    
U.S. Government Agencies [Member]
     
Investment Securities [Line Items]      
Period debt obligations mature, years, maximum 1 year    
Municipal Bonds [Member]
     
Investment Securities [Line Items]      
Period debt obligations mature, years, maximum 1 year    
Cumulative unrealized losses on municipal bonds $ 500,000