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Commitments and Contingencies - Additional Information (Detail)
$ in Millions
12 Months Ended
Sep. 28, 2016
USD ($)
Hospital
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Commitment And Contingencies [Line Items]        
Term of lease period   30 years or more    
Lease and Rental Expenses   $ 9.8 $ 6.8 $ 4.6
Sublease rental income   $ 6.6 $ 4.2 $ 2.3
Washington [Member] | Acute Care Hospital [Member]        
Commitment And Contingencies [Line Items]        
Number of facilities acquired | Hospital 1      
Purchase price of acquisition $ 17.5