XML 58 R40.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 08, 2015
Summary Of Significant Accounting Policies [Line Items]        
Sale of minority interest percentage 75.00%      
Cash and cash equivalents maturity description   90    
Additional amounts to be paid in cash or common stock based on achievement of performance measures within period, maximum years   5 years    
Money market funds fair value   $ 9.2 $ 12.4  
Cash surrender fair value of life insurance   15.6 15.8  
Contingent consideration liabilities related to acquisitions   $ 30.5 $ 17.3  
5.25% Senior Unsecured Notes Due 2023 [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Debt instrument interest rate       5.25%
Unnamed Corporate Joint Venture [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Equity method ownership percentage in joint venture   37.50%    
Government Contracts Concentration Risk [Member] | Accounts Receivable [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Percentage of net accounts receivable   17.00% 17.00%  
Buildings [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   30 years    
Maximum [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Long-term investments maturity period, in years   6 years    
Short-Term investments maturity period, in years   1 year    
Intangible assets finite lives   20 years    
Maximum [Member] | Medical Equipment [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   7 years    
Maximum [Member] | Computer Equipment [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   7 years    
Maximum [Member] | Software and Software Development Costs [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   7 years    
Maximum [Member] | Furniture [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   7 years    
Minimum [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Long-term investments maturity period, in years   1 year    
Intangible assets finite lives   1 year    
Minimum [Member] | Medical Equipment [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   3 years    
Minimum [Member] | Computer Equipment [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   3 years    
Minimum [Member] | Software and Software Development Costs [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   3 years    
Minimum [Member] | Furniture [Member]        
Summary Of Significant Accounting Policies [Line Items]        
Property and equipment estimated useful lives, years   3 years