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Summary of Significant Accounting Policies (Narrative) (Detail) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 12 Months Ended
Jan. 01, 2009
Dec. 31, 2012
Y
Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]      
Long-term investments maturity, minimum years   1  
Long-term investments maturity, maximum years   6  
Additional cash amounts to be paid based on achievement of performance measures within period, maximum years 5 years    
Intangible assets finite lives, maximum years   1 year 10 months 24 days  
Money market funds carrying amount   $ 11.1 $ 11.6
Cash surrender value, fair value   13.8 12.7
Contingent consideration liabilities related to acquisitions   $ 37.7 $ 32.4
Government Contracts Concentration Risk [Member] | Accounts Receivable [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Percentage of net accounts receivable   21.00% 23.00%
Minimum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Intangible assets finite lives, maximum years   1 year  
Maximum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Intangible assets finite lives, maximum years   20 years  
Buildings [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   20 years  
Medical Equipment [Member] | Minimum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   3 years  
Medical Equipment [Member] | Maximum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   10 years  
Computer Equipment [Member] | Minimum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   3 years  
Computer Equipment [Member] | Maximum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   10 years  
Software [Member] | Minimum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   3 years  
Software [Member] | Maximum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   10 years  
Furniture [Member] | Minimum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   3 years  
Furniture [Member] | Maximum [Member]
      
Summary Of Significant Accounting Policies [Line Items]      
Property and equipment estimated useful lives, years   10 years