|**Accounts Receivable (Tables)**       | 12 Months Ended                                                                                                                                                                                                                                               
|-------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|**Receivables [Abstract]**             |                                                                                                                                                                                                                                                               
|Schedule of Accounts Receivable        | Accounts receivable consists of the following (in millions):As of December 31,20182017Current:Patient accounts receivable$459.9$459.5Other accounts receivable7.812.6467.7472.1Noncurrent patient accounts receivable155.5129.1Accounts receivable$623.2$601.2
|                                      
|                                       |                                                                                                                                                                                                                                                               
|                                       | As of December 31,                                                                                                                                                                                                                                            
|                                       | 2018                                                                                                                                                                                                                                                          
|Current:                               |                                                                                                                                                                                                                                                               
|Patient accounts receivable            | $                                                                                                                                                                                                                                                             
|Other accounts receivable              | 7.8                                                                                                                                                                                                                                                           
|                                       | 467.7                                                                                                                                                                                                                                                         
|Noncurrent patient accounts receivable | 155.5                                                                                                                                                                                                                                                         
|Accounts receivable                    | $                                                                                                                                                                                                                                                             

X- ReferencesNo definition available.
+ Details**Name:**
us-gaap_ReceivablesAbstract**Namespace Prefix:**
us-gaap_**Data Type:**
xbrli:stringItemType**Balance Type:**
na**Period Type:**
duration X- DefinitionTabular disclosure of the various types of trade accounts and notes receivable and for each the gross carrying value, allowance, and net carrying value as of the balance sheet date. Presentation is categorized by current, noncurrent and unclassified receivables.
+ ReferencesReference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3,4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
+ Details**Name:**
us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTextBlock**Namespace Prefix:**
us-gaap_**Data Type:**
nonnum:textBlockItemType**Balance Type:**
na**Period Type:**
duration