Segment and Geographic Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018 Hospital
Segment Reporting Information [Line Items]
Number of geographically organized groups	2
Number of owned and operated hospitals	179
Reorganization Group [Member] | National Group [Member]
Segment Reporting Information [Line Items]
Number of owned and operated hospitals	88
Reorganization Group [Member] | American Group [Member]
Segment Reporting Information [Line Items]
Number of owned and operated hospitals	85
Reorganization Group [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Number of owned and operated hospitals	6