Segment and Geographic Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 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	87
Reorganization Group [Member] | American Group [Member]
Segment Reporting Information [Line Items]
Number of owned and operated hospitals	86
Reorganization Group [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Number of owned and operated hospitals	6