Significant Accounting Policies - Goodwill and Intangible Assets (Details) - USD ($)
 12 Months Ended
Oct. 01, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Intangible Assets [Line Items]        
Goodwill impairment $ 0 $ 0 $ 0 $ 0
Physician Income Guarantees | Minimum        
Intangible Assets [Line Items]        
Intangible asset useful life   3 years    
Physician Income Guarantees | Maximum        
Intangible Assets [Line Items]        
Intangible asset useful life   4 years    
Non-Compete Agreements | Minimum        
Intangible Assets [Line Items]        
Intangible asset useful life   2 years    
Non-Compete Agreements | Maximum        
Intangible Assets [Line Items]        
Intangible asset useful life   20 years    
Management Rights        
Intangible Assets [Line Items]        
Intangible asset useful life   15 years    
Customer Relationships | Minimum        
Intangible Assets [Line Items]        
Intangible asset useful life   3 years    
Customer Relationships | Maximum        
Intangible Assets [Line Items]        
Intangible asset useful life   10 years