Quarterly Results - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Quarterly Financial Information [Line Items]
After tax reduction per diluted share pursuant to tax cuts and jobs act 2007	$ 30,000,000
After tax reduction per diluted share pursuant to tax cuts and jobs act 2007	$ 0.32
River Point Behavioral Health | Located in U.K.
Quarterly Financial Information [Line Items]
Unfavorable after tax reduction pursuant to tax cuts and jobs act 2007	$ 11,300,000
Tax reduction per diluted share pursuant to tax cuts and jobs act 2007	$ 0.12
River Point Behavioral Health | Located in Puerto Rico
Quarterly Financial Information [Line Items]
Unfavorable after tax reduction pursuant to tax cuts and jobs act 2007	$ 11,300,000
Tax reduction per diluted share pursuant to tax cuts and jobs act 2007	$ 0.12
ASU 2016-09
Quarterly Financial Information [Line Items]
Favorable after tax impact	$ 13,500,000	$ 487,000	$ 1,400,000	$ 6,800,000
Favorable after tax impact per share diluted	$ 0.14	$ 0.01	$ 0.01	$ 0.07
EHR Applications
Quarterly Financial Information [Line Items]
Unfavorable pre-tax reduction	$ 3,600,000	$ 4,200,000	$ 6,400,000	$ 8,100,000	$ 2,800,000	$ 8,500,000	$ 8,700,000	$ 8,300,000
Unfavorable after-tax reduction	$ 2,300,000	$ 2,600,000	$ 4,000,000	$ 5,100,000	$ 1,800,000	$ 5,300,000	$ 5,500,000	$ 5,200,000
Tax reduction per diluted share	$ 0.03	$ 0.03	$ 0.04	$ 0.05	$ 0.02	$ 0.06	$ 0.05	$ 0.05