Segment Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 Beds State Facilities
Segment Reporting Information [Line Items]
Number of facilities | Facilities	582
Number of beds | Beds	17,800
Number of operating states | State	39
U.S. Facilities [Member]
Segment Reporting Information [Line Items]
Number of facilities | Facilities	209
Number of beds | Beds	8,900
Number of operating states | State	39
U.K. Facilities [Member]
Segment Reporting Information [Line Items]
Number of facilities | Facilities	373
Number of beds | Beds	8,900