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Property and Equipment - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Property, Plant and Equipment [Line Items]      
Depreciation expense for continuing operations $ 79,100,000 $ 76,600,000 $ 67,800,000
Depreciation expense for discontinued operations 300,000 1,800,000 2,600,000
Asset impairment charges 30,500,000    
Gain on sale of property (301,000) 1,711,000 (457,000)
Property and Equipment [Member]
      
Property, Plant and Equipment [Line Items]      
Asset impairment charges 30,500,000   300,000
Teach Out Schools [Member]
      
Property, Plant and Equipment [Line Items]      
Asset impairment charges 29,500,000    
California [Member]
      
Property, Plant and Equipment [Line Items]      
Gain on sale of property   1,400,000  
Leased Facilities [Member]
      
Property, Plant and Equipment [Line Items]      
Asset impairment charges $ 1,000,000   $ 300,000