Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018 Facility Bed State
Segment Reporting Information [Line Items]
Number of facilities | Facility	583
Number of beds | Bed	18,100
Number of operating states | State	40
U.S. Facilities [Member]
Segment Reporting Information [Line Items]
Number of facilities | Facility	213
Number of beds | Bed	9,300
Number of operating states | State	40
U.K. Facilities [Member]
Segment Reporting Information [Line Items]
Number of facilities | Facility	370
Number of beds | Bed	8,800